Ever had a bank ask why you're moving a large sum, hold a deposit for days, or close an account with little explanation? The rules behind those moments just produced one of the year's biggest bank penalties.

What happened

On October 8, the Office of the Comptroller of the Currency (OCC), which supervises national banks, fined American Express National Bank $350 million and issued a cease-and-desist order, PYMNTS reported. The OCC found the bank had not kept an adequate anti-money-laundering program.

The regulator cited three problems: too few resources devoted to compliance, a risk assessment that didn't match the bank's actual business, and what it called systemic breakdowns in monitoring and reporting suspicious activity.

The Federal Reserve issued its own cease-and-desist order against the parent company and its travel-services unit. It carries no fine, but it requires the company to fix its company-wide program.

Amex CEO Stephen Squeri said in a statement that the company has "made meaningful progress" and "there is more work to do." The company settled without admitting the findings, and it said the penalty does not change its full-year financial guidance.

Comptroller Jonathan Gould said the OCC expects banks of Amex's size and complexity to put enough resources into anti-money-laundering compliance.

The rules behind the fine

The core law is the Bank Secrecy Act (BSA), passed in 1970. It requires banks to know who their customers are, watch for transactions that could involve money laundering or other crimes, and report them to the Treasury Department's Financial Crimes Enforcement Network, known as FinCEN.

In practice, that means three things every customer runs into:

Identity checks. Banks must verify who you are when you open an account. This is the "know your customer" process.

Monitoring. Software and analysts watch for unusual patterns, such as sudden large transfers, frequent cash deposits just under reporting thresholds, or money moving quickly through an account.

Reporting. Cash transactions over $10,000 trigger a currency transaction report. Activity that looks suspicious triggers a suspicious activity report (SAR), which banks are legally barred from discussing with the customer involved.

That last rule is why a bank that closes an account over compliance concerns often won't tell you why. It may not be allowed to.

Why it matters

Penalties like this ripple outward. When a large bank is fined for weak monitoring, the whole industry tends to tighten up. Compliance teams add reviews, flag more transactions and lower their tolerance for unusual activity.

That has a cost for ordinary customers. Small businesses that handle a lot of cash, people who send money abroad to family, and anyone whose transactions look unusual are more likely to hit delays or questions. It's a trade-off regulators and banks have argued about for years: stronger controls catch more crime, but they also catch more innocent people in the net.

This case also stands out because it involves a card-focused bank, not a traditional branch bank. Regulators are signaling that every type of bank is expected to keep up.

What you can do

Keep records for large or unusual transactions, such as a home sale, an inheritance or a business payment, so you can explain them if asked.

Avoid splitting cash deposits to stay under $10,000. Breaking up deposits to avoid a report is called structuring, and it's a federal crime on its own, even if the money is legitimate.

Respond promptly if your bank asks for information. Unanswered requests can lead a bank to restrict or close an account.

If your account is closed, ask for any balance to be returned by check, and file a complaint with the bank's regulator if you believe you were treated unfairly.

What to watch

The Fed's order requires Amex to submit written plans to fix its program. Watch whether other large card issuers face similar scrutiny.

Sources: PYMNTS (Oct. 8) · Federal Reserve enforcement action (Oct. 8) · American Express statement

Beyond the Bank is for informational purposes only and is not financial, legal, or investment advice.

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