IB doesn't know when customer checks actually clear. IB has a corporate account and our bank credits corporate accounts based on the expected clearing date of the check. IB's bank uses ABA routing numbers as a proxy to determine how long it will take a check to clear. For example, IB will receive value on a check drawn on a New York bank faster than it will receive value on a check drawn on a California bank.
Check processing speed has improved because of system developments other than Check 21. However, the return check process does not seem to have improved yet. When the maker's bank receives a check for payment it either provides payment or submits notification to the payee's bank that it will not honor the check for payment because of non-sufficient funds, closed account etc. IB's bank receives the notification of a returned check via the Federal Reserve and deducts the funds from IB's bank account since it originally credited IB based on an estimated funds availability schedule (not when the check actually clears). IB then reverses the funds to its customer's IB account. There is no set time frame for returned checks and IB has experienced returned checks up to seven business days.
Before IB implemented the seven-business day hold period, it experienced losses from returned checks. IB wishes to keep its commissions as low as possible and therefore it avoids preventable losses. We encourage our customers to send funds via bank check or wire if they require immediate availability of funds.