Earlier quoted context omitted.
> The only things that are checked are the digits of the amount, and the account number. Well, the payee is also usually verified to match the destination account, and a few other elements are technically required for it to be a legal financial instrument (even if banks don't spend the time to check them every time). Legally, a check could be written on the back of a napkin and still be valid - as long as it has a fe…
> It inherently relies on the legal system to sort things out after the fact, ... This is why it’s critical to have transaction alerts for all activity for your financial accounts. Otherwise you could have an ACH slip through that drains your account. You wouldn’t notice till the next time you logged in or, more likely, when you try to use your debit card and realize it’s cleaned out.
Often times banks will set these limits unnecessarily high ($10K is common). Alerts are a good way to spot the fraud, but limits cap how much they can take in the mean time. Even if you will ultimately get refunded, it could take months of a slow investigation before that occurs.
I have mine set to double the most we've ever spent in a single month, and I've only had to increase it once (vehicle downpayment).