CASH HANDLING ACCURACY and FINANCIAL INTEGRITY are absolute requirements for USPS customer service roles. There is only one correct response to recognizing a cash handling error: correct it immediately and transparently.
Immediate correction: (1) Call the customer back before they leave the premises — 'Excuse me, I made an error in your change; can I get you to come back to the window?'; (2) Count the correct change aloud so both you and the customer can verify; (3) Acknowledge the error simply: 'I apologize — I gave you change for $30 instead of $50'; (4) Correct the error completely: the customer should receive the additional $20.25 they are owed.
Why transparency is mandatory: The error works in the customer's favor — this is not a situation where you are protecting yourself; this is about doing what is right; postal employees are subject to strict standards of financial accountability; intentional misappropriation of even small amounts is grounds for termination and possible prosecution; an uncorrected cash discrepancy will appear when the cash drawer is counted at end of shift — better to document the error than to have an unexplained shortage/overage; USPS mystery shoppers and cash drawer audits catch cash handling errors.
About hesitation: in this scenario, there is no ambiguity — you KNOW the error occurred and which direction it went; hesitation or hoping the customer doesn't notice is a form of dishonesty.
Pattern errors: if you find yourself making repeated cash handling errors, report this to your supervisor so you can receive additional training; this is better than accumulating errors that damage your record and customers' trust.