Q.
How do automated teller machines know the amount of a deposited check without me entering the numbers on the keypad?
A.
Most bank A.T.M.s automatically scan a high-resolution image of the check when you insert it into the deposit slot. This check image is processed with optical character recognition (O.C.R.) software, which reads the amount of money printed on the check. The A.T.M. also reads account and routing numbers encoded in the magnetic ink on the check. This is why checks printed with standard home inkjet printers are usually rejected.
Mistakes can still happen due to smudged originals and other issues. If the check's amount does not match the amount on your receipt, contact the bank's customer-service department.
A version of this article appeared in print on 05/09/2013, on page B10 of the NewYork edition with the headline: Scanning Checks At the A.T.M..