Bank adjustments are done on checking and savings accounts to correct errors in deposits or withdrawals. Banks do not need your permission to make an adjustment, and you might not even be aware one has happened until you notice the adjustment listed on your account statement.
A check you deposited can be sent back for numerous reasons, and the amount initially credited to your account will be deducted once an adjustment has been made. Among the reasons for deposit errors: You forgot to endorse the check, the account the check was drawn on has been closed, the check issuer put a stop payment on the check or the check has missing or illegible magnetic ink character recognition numbers and the bank cannot process the check. In some cases, the amount of your deposit may have been entered incorrectly and an adjustment is needed to enter the correct amount.
Sometimes the bank may mistakenly withdraw money from your account. In such a case, the bank will do an adjustment to correct the mistake and return the funds to your account. Withdrawal mistakes are less common than deposit errors.