If IRS didn't send you a letter indicating a change, see if you decided to have IRS retain part of the refund to be applied to the next year's taxes. It would be noted on the 1040 you submitted.
https://ttlc.intuit.com/questions/2792575-i-want-to-apply-refund-to-estimated-taxes
https://ttlc.intuit.com/questions/1901277-how-do-i-apply-my-refund-to-next-year-s-taxes
