ACH fraud: How to detect, prevent, & report (with examples)

ACH fraud happens when someone initiates an unauthorized electronic funds transfer through the ACH network. The mechanics are surprisingly simple. Fraudsters need just two pieces of information to attempt a withdrawal from your account. Your business bank account number and your bank routing number. With those digits, they can pull money as if they were you.

This simplicity is what makes ACH fraud particularly dangerous. Your account and routing numbers aren't secret. They're printed on every check you write. You share them with vendors, employees, and service providers. Once someone has these numbers, the only thing stopping them from draining your account is the detection software in place at your bank and your own vigilance.

ACH fraud differs fundamentally from credit card fraud. When someone makes a fraudulent business credit card charge, you can dispute it and usually get your money back quickly. The card company takes the hit while they investigate. But ACH transactions are direct bank transfers. Once that money leaves your account, getting it back requires cooperation from multiple banks and often law enforcement. You might wait weeks or months for resolution, if you get your money back at all.

Understanding ACH fraud starts with recognizing this basic reality. Criminals can attempt to steal directly from your bank account with information that's relatively easy to obtain. The question isn't whether someone will try. It's whether you'll be ready when they do.

ACH fraud is accelerating because more businesses rely on electronic payments than ever before. The shift away from paper checks seemed like pure progress. Faster payments, lower costs, better tracking. But every ACH transaction creates an opportunity for fraud. As transaction volumes grow, so do successful attacks.

The ACH process has vulnerabilities that fraudsters know how to exploit. Start with the time delay. ACH transactions typically take one to two business days to clear. That gap creates a window where criminals can initiate transfers and disappear. A fraudster might drain an account on Friday afternoon, knowing the victim won't notice until Monday. By then, the money has moved through multiple accounts and is often out of reach.

Transaction details in ACH payments are minimal. You get account numbers, amounts, and maybe a short description. There's no rich context about who's sending money or why. Banks struggle to distinguish legitimate transfers from fraudulent ones when all they see are numbers and brief text. Fraudsters keep transactions small and unremarkable, flying under automated detection thresholds.

Your banking information is everywhere. Account and routing numbers appear on every check. They're in vendor databases, payroll systems, and accounting software. They're in emails, invoices, and payment forms. One data breach at any company you've paid or that pays you can expose these numbers. Fraudsters buy lists of banking details on criminal forums for pennies per account. They can also pull these numbers from trash bins or phishing emails.

Detection often depends on customers noticing something wrong. Many banks still rely on account holders to spot and report unauthorized ACH debits. This puts the burden on businesses to constantly monitor their accounts. Midsized and small businesses make particularly attractive targets. Criminals assume correctly that these companies check their accounts less frequently and have fewer controls than large corporations.

The sophistication of attacks keeps increasing while the basic ACH infrastructure remains largely unchanged. Fraudsters use social engineering, malware, and insider knowledge to bypass what security exists. They study business patterns, learning when accounts have high balances and when finance teams are distracted. What started as opportunistic theft has become organized crime.

ACH fraud takes many forms, each with distinct patterns and methods. Recognizing these different attack types helps you spot threats before they succeed. The examples below are fictional scenarios that illustrate how each type of fraud typically unfolds.

Unauthorized ACH debits

This is the most direct form of ACH fraud. Criminals withdraw money from your account without permission after obtaining your account and routing numbers. They might find these numbers through data breaches, phishing campaigns, malware infections, or even by intercepting physical mail.

Example of this fraud

A restaurant owner discovers $8,000 missing from his business checking account one morning. Investigation reveals that someone retrieved a discarded deposit slip from the restaurant's dumpster. The fraudster used the account information to set up an ACH debit to their own account at another bank. By the time the owner noticed, the receiving account was closed and the money was gone. This example shows why regular account reconciliation and ACH debit blocks matter.

Phishing and credential theft

Fraudsters send emails or texts that appear to come from banks or trusted vendors. These messages create urgency around account problems or security issues. When employees click the links and enter their credentials, criminals capture everything they need to access online banking.

Example of this fraud

An accounts payable manager receives an email that looks exactly like her bank's standard security alerts. It warns that suspicious activity requires immediate verification. She clicks through and enters her username and password on what looks like the bank's website. The attackers now have full access to the company's operating accounts. They wait until Friday evening, then initiate multiple ACH transfers totaling $75,000. This illustrates why you should always verify suspicious emails by calling your bank directly, never through links in the message.

Account takeover fraud

This goes further than stealing passwords. Criminals gain complete control of your bank account by obtaining valid credentials and bypassing security measures. They might use information from data breaches, deploy keyloggers, or buy credentials on criminal markets. Once inside, they can schedule transfers that look legitimate to your bank's systems.

Example of this fraud

A manufacturing company discovers $50,000 missing from their reserve account. Forensic analysis shows that attackers used credentials exposed in an unrelated data breach six months earlier. The criminals logged in during overnight hours, when no legitimate users would notice. They transferred funds via ACH to accounts they controlled, then moved the money overseas. Multifactor authentication on all banking access would have stopped this attack.

Business email compromise and payment redirection

BEC scams involve impersonating executives or trusted partners to redirect legitimate payments. Fraudsters research your organization, learning names, projects, and payment patterns. They craft emails that reference real situations but change the payment details.

Example of this fraud

An accounting clerk receives an email from what appears to be the CEO's address. It references a real acquisition the company is pursuing and requests an urgent $25,000 payment to secure legal documents. The email includes ACH details for the supposed law firm. The clerk, knowing the acquisition is real, processes the payment immediately. The money goes straight to fraudsters. This scenario demonstrates why you should always verify payment changes through a second communication channel.

Fake vendor invoices

Criminals send invoices that look identical to those from your regular vendors, but with different payment information. They might compromise a vendor's email account or create lookalike domains. The invoice appears routine, so it gets paid without scrutiny.

Example of this fraud

A hospital's finance department receives an invoice from their medical supply vendor. Everything looks normal except for a small note about updated banking information. The amount matches their usual monthly order. They process the ACH payment without calling to verify. Three weeks later, the real vendor calls about the overdue invoice. The hospital sent $45,000 to criminals. Any change in payment instructions requires verbal confirmation with established contacts.

Payroll diversion

Scammers redirect employee paychecks by submitting fake direct deposit changes. They might hack employee email accounts, compromise HR portals, or impersonate workers over the phone.

Example of this fraud

An employee at a tech startup doesn't receive her direct deposit on payday. HR investigation finds that someone submitted a direct deposit change form two weeks earlier using her employee ID and basic information. The company sent two paychecks totaling $8,500 to a fraudster's account. The criminal used information from the employee's social media to answer security questions. This shows why companies need multiple forms of verification for any payroll banking changes.

ACH kiting

Fraudsters exploit the float time between ACH initiation and settlement. They cycle the same funds through multiple accounts, creating artificial balances they can withdraw before the transfers fail.

Example of this fraud

A scammer opens accounts at three different banks using synthetic identities. He initiates a $10,000 ACH transfer from Bank A to Bank B late Thursday. Friday morning, before the transfer settles, he moves the provisional credit from Bank B to Bank C. He then withdraws cash from Bank C before any of the transfers clear. When everything bounces Monday morning, he has extracted $10,000 that never existed. Banks now use pattern detection to spot these round trip transfers.

Ghost payments and fake ACH credits

Some platforms credit customer accounts before ACH transfers fully clear. Fraudsters exploit this by initiating transfers they know will fail, then quickly converting the temporary credits to irreversible assets.

Example of this fraud

A crypto trading platform allows instant deposits via ACH for customer convenience. A fraudster initiates a $5,000 transfer from an account with insufficient funds. The platform credits the $5,000 immediately. Within minutes, the fraudster buys cryptocurrency and transfers it to an external wallet. Three days later, the ACH transfer bounces. The platform loses the full amount with no recourse. Financial platforms must balance customer convenience with settlement risk.

Insider fraud

Employees or contractors with system access can initiate fraudulent transfers themselves. They might create phantom vendors, submit duplicate payments, or simply transfer money to their own accounts.

Example of this fraud

A bookkeeper at a nonprofit sets up a fake vendor in the accounting software. Over six months, she approves $30,000 in ACH payments to this vendor, which is actually her personal account at an online bank. She covers the theft by miscategorizing the expenses across multiple budget lines. Only an annual audit reveals the pattern. Separation of duties and regular audits can catch insider fraud before it grows.

Liability for ACH fraud depends on account type, security protocols, and timing. Business accounts operate under UCC Article 4A and individual banking agreements that let banks avoid liability if they followed commercially reasonable security procedures. This means businesses bear the loss unless they can prove the bank failed its obligations. If your employee fell for a phishing email, you authorized the payment through your agent, so you're liable. If malware compromised your credentials, that's your problem unless you can show the bank's software for the process was breached. Banks successfully argue that most business ACH fraud results from customer side failures rather than bank negligence.

Real scenarios show how liability gets assigned. When a business email compromise leads to fraudulent ACH payment, the business bears the loss because an authorized employee initiated the transfer, even under false pretenses. The transfer came from legitimate credentials, and courts don't care that the employee was tricked. For unauthorized debits where hackers initiate ACH pulls without employee involvement, the bank might be liable only if the business reports within their agreement's narrow window and the bank failed reasonable security measures. Miss that one or two day deadline and liability shifts entirely to the business. The receiving bank faces potential liability through NACHA's return rules and must return funds if notified promptly, even if the fraudster's account is empty. But wait too long and this protection disappears.

The entire liability structure punishes delays and rewards quick detection. Businesses that don't monitor accounts daily or lack proper controls end up liable by default. Courts repeatedly uphold these arrangements, finding that businesses must bear fraud losses when they fail to implement available security measures or miss reporting deadlines. The process assumes businesses have resources for fraud prevention, then assigns liability accordingly. Your business can't rely on others to absorb fraud losses. The liability will probably land on you unless you can prove someone else clearly failed their duties. This harsh reality makes prevention essential since recovering losses through liability claims rarely succeeds.

Detecting ACH fraud early can mean the difference between a minor incident and a major loss. Finance teams that know these warning signs can spot fraud attempts before they succeed. Each red flag below deserves immediate attention and investigation.

Unusual payment requests

Any sudden request to send money to a new recipient or unfamiliar bank account should trigger scrutiny. This includes vendors who've always accepted checks suddenly demanding ACH payments, or established suppliers requesting payment to different banks. Watch for requests that bypass normal approval chains or come through unusual channels.

These requests often arrive with explanations that seem plausible but don't quite fit. A vendor might claim they're switching banks due to "security upgrades" or "system maintenance." The amounts might match typical transactions, making them seem legitimate. But any deviation from established payment patterns warrants a phone call to verify.

Urgency or secrecy

Fraudsters manufacture urgency to short circuit your normal review processes. They'll claim payments must happen today to avoid penalties, secure deals, or meet deadlines that somehow just appeared. They'll insist on confidentiality, saying the CEO wants this handled quietly or that discussing it could jeopardize a sensitive negotiation.

Real business rarely works this way. Legitimate urgent payments still follow procedures. Actual executives understand the importance of financial controls. When someone pushes you to act fast and skip steps, slow down instead. The few minutes you take to verify could save thousands.

Impersonation clues

Small details reveal fake communications. Email addresses that are one letter off from the real thing. Messages from the "CEO" that don't match their writing style. Vendors who suddenly communicate only through email when they've always called before. Grammar or spelling that seems off for professional communication.

Look closer at email headers and domains. Fraudsters create lookalike addresses that fool casual glances. They might use the CEO's name but send from a Gmail account. They reference real projects or people but get small details wrong. Training your eye for these inconsistencies becomes second nature with practice.

Account anomalies

Your bank accounts have patterns. Payments go out on certain days, in typical amounts, to regular recipients. When transactions break these patterns, pay attention. This includes ACH transfers at 2 AM when your business closes at 5 PM, or payments from IP addresses in countries where you have no operations.

Small test transactions deserve particular scrutiny. Fraudsters often send tiny amounts first to verify account access works. A mysterious $0.50 debit might seem like a rounding error, but it could signal that someone's preparing to drain your account. Set up alerts for any transaction outside normal parameters.

Multiple credits and quick withdrawals

Watch for accounts that suddenly receive numerous ACH credits from unrelated sources, followed by immediate withdrawals or transfers. This pattern often indicates an account being used as a money mule to launder stolen funds. Legitimate business accounts show predictable flows tied to actual operations.

The credits might come from individuals or businesses you don't recognize. The withdrawals happen fast, often within hours of credits posting. If your account shows this pattern, someone might be using it for fraud without your knowledge. Contact your bank immediately.

Duplicate or altered invoices

Receiving two invoices for the same service, invoices for services you didn't order, or familiar invoices with different banking details all signal potential fraud. Criminals count on busy finance teams paying without close inspection. They might send duplicates weeks apart, hoping you've forgotten the first payment.

Compare new invoices against previous ones from the same vendor. Look for changes in format, logo quality, or payment terms. Check invoice numbers for sequence. Real vendors have consistent invoicing processes. Fraudulent invoices often have subtle inconsistencies that reveal their fake nature.

Employee reports of missing payments

When employees report missing paychecks or vendors call about overdue payments you thought you made, investigate immediately. These complaints often reveal that money went somewhere other than intended. The sooner you discover misdirected payments, the better your recovery chances.

Don't dismiss these reports as administrative errors. Pull the transaction records immediately. Verify where the money actually went. If payments were diverted, you need to act within hours, not days, to have any hope of recovery.

Banks reimburse ACH fraud under specific circumstances that vary dramatically between consumer and business accounts. The short answer is that consumers usually get their money back, while businesses usually don't. This disparity stems from different legal frameworks and the assumption that businesses have resources to implement their own fraud controls.

Consumer protection laws require banks to make individual account holders whole for unauthorized ACH transactions. Under Regulation E, if you report the fraud within 60 days of receiving your statement, the bank must investigate and typically reimburse you within 10 business days. The bank might provide provisional credit even sooner while investigating. These protections recognize that individual consumers lack the sophistication and resources to prevent sophisticated fraud. The bank absorbs the loss as a cost of doing business in the consumer market.

Business accounts tell a different story. No federal law mandates that banks reimburse businesses for ACH fraud. Instead, the Uniform Commercial Code Article 4A and individual banking agreements govern these situations. These rules typically state that if the bank followed agreed security procedures, the business bears the loss. Banks often require businesses to report fraud within one or two business days. Miss that window and the bank will almost certainly deny your claim. Even when reported promptly, banks usually only attempt to recover funds rather than guarantee reimbursement. They might provide provisional credit while filing an ACH return, but if recovery fails, that credit gets reversed and the business eats the loss.

The practical implications are stark. A consumer whose account gets drained by fraudsters will likely see full reimbursement within days. A business suffering the same attack might never recover a penny. Some banks voluntarily cover small losses to maintain customer relationships, but they're not obligated to do so. This reality makes fraud prevention essential for businesses. You can't count on your bank to save you from ACH fraud. The safer approach involves implementing ACH positive pay, debit blocks, dual approvals, and daily monitoring to prevent unauthorized transactions entirely. Think of bank reimbursement as a safety net with massive holes for business accounts. It might catch you, but you shouldn't count on it.

ACH fraud inflicts damage that extends far past the stolen funds. Knowing the full scope of potential harm helps justify the investment in prevention. When fraud strikes, businesses face immediate financial loss, operational chaos, damaged relationships, and sometimes legal consequences that linger for years.

Financial losses

The numbers are stark. In 2024, 38% of businesses experienced ACH debit fraud, while 20% faced ACH credit fraud. These aren't minor incidents. Single fraudulent transactions routinely reach six figures. One FBI case documented a company losing $840,000 through an ACH diversion scam. For smaller businesses, even a $50,000 loss can mean missing payroll, defaulting on loans, or shutting down operations.

Recovery rates disappoint. Unlike credit card chargebacks, ACH fraud reversals require cooperation from multiple banks and happen only under specific circumstances. If the receiving bank won't cooperate or the funds have already been withdrawn, that money is gone. Insurance might help, but policies often have exclusions and deductibles that leave businesses absorbing substantial losses.

The indirect costs add up quickly too. Forensic investigations, legal fees, and enhanced security measures after an incident can match or exceed the original theft. A $100,000 fraud might trigger $200,000 in total costs by the time everything resolves.

Operational disruption

When fraud hits, normal business stops. Finance teams drop everything to investigate transactions, file reports, and secure accounts. IT scrambles to check for breaches and implement emergency security measures. Management spends days in crisis meetings instead of running the company.

Companies hit by ACH fraud often lose millions and face immediate operational paralysis. Vendor payments must halt until legitimate transactions can be verified. Payroll processing freezes, leaving employees without paychecks while new procedures are established. Customer orders remain unfulfilled because no one knows which accounts are compromised. The entire organization shifts from normal business operations to full-time fraud response and recovery mode.

The disruption ripples outward. Projects stall without funding. Contracts get delayed while legal reviews payment terms. Growth initiatives freeze because nobody trusts the financial processes in place. Some businesses never fully recover their operational momentum after a major fraud event.

Reputational damage

Trust takes years to build and moments to destroy. When clients learn their payments were misdirected or their data might be compromised, confidence evaporates. Partners question whether you can handle their business securely. Investors wonder about your internal controls.

Market research shows consumers avoid organizations they don't trust with financial data. One merchant survey found that a third of compliance professionals cite reputational risk as the primary driver for security improvements. They know that public fraud incidents trigger customer defections that can devastate revenue.

The damage spreads through whisper networks before any public announcement. Vendors talk to other vendors. Customers share warnings in industry forums. Your fraud incident becomes a cautionary tale told at conferences and board meetings. Rebuilding that reputation requires years of perfect execution and substantial marketing investment.

Legal and regulatory consequences

Fraud incidents trigger scrutiny from multiple directions. If customer funds were lost, you might face lawsuits from affected parties. Regulatory bodies investigate whether you maintained adequate controls. State authorities examine potential data breach notifications requirements.

Failing to maintain proper ACH controls can create liability. Courts have found companies negligent for not implementing available security measures. If your lax procedures enabled fraud that harmed others, you might bear legal responsibility for their losses. These cases drag on for years and generate massive legal bills regardless of outcome.

Regulatory penalties add insult to injury. Financial institutions and money transmitters face fines for inadequate fraud controls. Even nonfinancial businesses might violate data protection laws if fraud exposed customer information. Compliance costs skyrocket as regulators demand enhanced procedures and regular audits going forward.

Long term business impact

Many businesses never fully recover from major ACH fraud. The immediate cash loss might force delayed payments to critical vendors. Those delays damage credit ratings, making future financing more expensive. Key employees might leave for more stable companies. Customers who defected during the crisis don't return.

The psychological impact on teams shouldn't be underestimated. Employees who fell for phishing attacks carry guilt. Finance teams become paralyzed by indecision, scared to process legitimate payments. The organization develops a culture of fear rather than productive caution. Innovation stalls as all risk taking stops.

Some companies emerge stronger, with better controls and hard won wisdom about security. But they're the exceptions. Most businesses that suffer major ACH fraud face years of reduced growth, higher costs, and limited opportunities. The stolen money was just the beginning of their losses.

Recovering stolen funds from ACH fraud depends on three factors. How fast you act, what type of account you have, and whether the money still exists somewhere retrievable. Business accounts face an uphill battle that consumer accounts don't. Time destroys your recovery chances. Consumers get up to 60 days under federal law to report unauthorized ACH transactions. Businesses get as little as 24 hours under many bank agreements. The moment you discover fraud, start the clock. Your bank needs immediate notification to freeze accounts and initiate reversals. Every hour you wait reduces the chance that funds remain in the fraudster's account.

Consumer accounts enjoy strong legal protections under Regulation E, which requires banks to reimburse unauthorized electronic transfers. Business accounts operate under completely different rules. The Uniform Commercial Code Article 4A and individual bank agreements generally favor banks, not businesses. Banks can shift liability to businesses if the company failed to follow agreed security procedures or missed reporting deadlines. If your employee fell for a phishing email or you didn't report fraud within one business day, you're probably eating the loss. Banks might provide provisional credits during investigation, but they'll reverse those credits if recovery fails.

Your bank initiates recovery through ACH returns or reversal requests sent to the receiving bank. Success depends entirely on whether funds remain in the destination account. The receiving bank must return fraudulent transfers if notified quickly enough, but they can't return money that's already gone. While your bank handles the official recovery process, consider contacting the receiving bank directly to flag the fraud. Sometimes direct notification gets accounts frozen faster. Work both formal and informal channels, providing transaction details and emphasizing urgency.

When banks deny reimbursement claims, explore alternatives immediately. Cyber insurance might cover losses that banks won't reimburse. File reports with local police, the FBI's IC3, and the FTC to create official records for insurance claims and tax deductions. Legal action sometimes succeeds if the bank didn't follow commercially reasonable security procedures. Review your insurance coverage before you need it, understanding what documentation claims require. The harsh reality is that businesses rarely recover ACH fraud losses unless they act within hours and have either strong insurance coverage or clear evidence of bank negligence. Prevention remains far more reliable than recovery.

Prevention costs far less than recovery. Every dollar spent on ACH fraud prevention saves potentially hundreds in losses and response costs. The most successful approaches layer multiple defenses, making fraud attempts difficult enough that criminals move on to easier targets.

Employee education and training

Your employees are either your strongest defense or your weakest link. Most ACH fraud starts with human error. Someone clicks a phishing link, believes a fake vendor, or bypasses procedures for convenience. Regular training transforms employees into fraud detectors rather than victims.

Make training practical, not theoretical. Show real phishing emails your industry receives. Walk through actual fraud attempts step by step. Run surprise simulations where you send fake phishing messages and see who clicks. Those who fall for it get immediate additional training, not punishment. The goal is learning, not blame.

Focus on specific behaviors. Employees should never share banking credentials, even with someone claiming to be their boss or IT support. They should verify any payment change request through a second channel. They should report suspicious requests immediately, even if they're not sure. Keep messages fresh through varied formats and recent examples that maintain engagement.

Strong authentication controls

Passwords provide minimal security. Anyone who captures or guesses a password can drain your accounts. Multifactor authentication makes unauthorized access exponentially harder.

Implement MFA on all financial software, not just banking portals. Your accounting software, payment platforms, and HR software all need protection. Use authenticator apps or hardware tokens rather than SMS codes, which fraudsters can intercept through SIM swapping.

Control access ruthlessly. Only employees who absolutely need ACH initiation rights should have them. Everyone else gets read only access or no access at all. Review permissions quarterly. When employees leave or change roles, revoke access immediately. That contractor who helped with year end close doesn't need permanent access to your banking.

Consider time based restrictions. Maybe ACH transfers can only happen during business hours from recognized IP addresses. After hours attempts get blocked automatically. Geographic restrictions add another layer. If you operate only in Ohio, block access attempts from overseas. These simple rules stop many automated attacks.

Dual approval and transaction limits

No single person should control money movement. Dual approval requirements mean fraudsters need to compromise two employees or convince two people to fall for the same scam. Those odds favor you.

Structure approvals based on risk. Payments under $1,000 to established vendors might need one approval. New payees always require two approvals regardless of amount. Payments over $10,000 need two approvals plus a phone confirmation. International transfers require written documentation and executive sign off.

Set hard limits that technology enforces. Daily ACH limits prevent catastrophic losses even if all other controls fail. Individual transaction limits force fraudsters to attempt multiple transfers, increasing their detection risk. Account maximum balances limit exposure by automatically sweeping excess funds to protected accounts.

Make exceptions difficult. That urgent request to bypass dual approval for a critical payment? It still needs documentation, a phone call to verify, and retroactive review. True emergencies are rare. Most "urgent" requests are either poor planning or fraud attempts.

Bank ACH fraud prevention tools

Banks offer powerful fraud prevention tools that many businesses never activate. These services stop fraud attempts before money leaves your account. ACH debit blocks and filters give you control over incoming debits. With blocks, you reject all ACH debits except those from pre approved sources. Filters let you review and approve each debit before it processes.

Positive Pay for ACH works like a guest list at an exclusive club. You tell the bank exactly which ACH transactions to expect. Anything else gets rejected or held for review. Universal Payment Identification Codes (UPIC) let you receive ACH credits without exposing your real account number. You give vendors your UPIC instead of account details. Fraudsters who steal a UPIC can't use it to initiate debits.

Talk to your bank about these services today. Some cost extra, but the protection they provide far exceeds the fees. Not all banks offer every service, so you might need to shop around. The right banking partner sees fraud prevention as a shared responsibility.

Secure banking procedures

Written procedures remove ambiguity and prevent shortcuts that enable fraud. Document exactly how payment changes get approved, who can authorize transfers, and what verification steps are required.

Vendor payment changes require special attention. Never accept emailed requests to change banking information. Call the vendor at a previously verified number to confirm. Send a test payment of a small amount and confirm receipt before sending full payments. Keep a secured list of verified vendor payment information that can't be altered without multiple approvals.

Payroll changes need similar protection. Require employees to submit direct deposit changes through a secure portal or in person. Send confirmation of any change to both the old and new contact information on file. If someone fraudulently changes another employee's direct deposit, the real employee gets alerted immediately.

Establish clear chains of command. The CEO calling directly to request a wire transfer? That request still goes through normal channels. Vendors claiming payment delays will cause service interruption? They still need proper verification. Procedures apply to everyone, always.

System and network security

Technical security protects the infrastructure that processes your ACH transactions. Weak IT security makes all other controls meaningless if fraudsters can simply hack in and take what they want.

Keep all systems updated. Those annoying security patches fix vulnerabilities that criminals actively exploit. Delay updates, and you're leaving doors open. Automate updates where possible so human forgetfulness doesn't create openings.

Encrypt sensitive data everywhere. Banking information in your accounting system needs encryption at rest. ACH files transmitted to banks need encryption in transit. Employee computers that access financial systems need full disk encryption. If fraudsters steal encrypted data, they get meaningless gibberish.

Restrict network access. Financial systems should be isolated from general business networks. Remote access requires VPN connections with additional authentication. Public WiFi should never touch banking systems. These network controls create barriers that frustrate attackers and protect your money.

Regular audits and reviews

Continuous improvement requires regular assessment. Monthly reviews of ACH activity reveal patterns and gaps. Quarterly audits ensure procedures are followed. Annual penetration testing shows whether your defenses actually work.

Review ACH transactions for patterns. Are you paying vendors you don't recognize? Have payment amounts gradually increased without explanation? Do certain employees always bypass procedures? These reviews often reveal fraud or weak controls before major losses occur. Test your controls deliberately by attempting unauthorized payments yourself to identify gaps.

Bring in outside eyes annually. External auditors see things you miss through familiarity. They know what other companies do better. Their recommendations might seem excessive, but they're based on seeing what happens when controls fail. Take their findings seriously.

ACH fraud isn't some distant threat that only happens to other companies. It's happening right now, to businesses that thought they were protected. The criminals targeting your ACH transactions have refined their methods through thousands of successful attacks. They know exactly how long they have before you'll notice. They know which excuses make finance teams bypass security procedures. They know your bank won't reimburse business losses.

But you now know their playbook too. You understand how unauthorized debits work, why business email compromise succeeds, and what makes payroll diversion possible. You can spot the warning signs of unusual payment requests, suspicious urgency, and account anomalies. You have specific steps to implement, from employee training to dual approvals to bank security tools. You know that when fraud strikes, every hour counts and that recovery depends more on speed than hope. Most importantly, you understand that prevention works while recovery rarely does.

The right financial platform makes ACH fraud prevention automatic rather than exhausting. Brex combines same-day ACH processing with built in spend management controls that stop fraud before it starts. Every corporate card transaction requires approval workflows you define. Business banking includes real time monitoring and instant alerts for suspicious activity. When payments are processed the same day, fraudsters lose the float time they depend on. When every transaction follows preset rules, there's no room for social engineering to succeed. Instead of juggling multiple systems and hoping they work together, you get unified protection that actually prevents losses.

Your business deserves better than crossing fingers and hoping criminals pick someone else. Sign up for Brex today.