Does paying off a credit card instantly boost my credit score?

It can help quickly, but not always instantly. Utilization updates when your card issuer reports your balance to the bureaus, typically once a month around your statement date, not the moment you pay. So a payoff might not show up for a few weeks. Once it reports, dropping your utilization to near zero on that card can raise your score noticeably, since utilization is about 30% of a FICO score.

Counterintuitively, letting a tiny balance (a few dollars) report on one card, rather than zero across all cards, can sometimes score marginally higher, though the difference is small. Don't close the card after paying it off, since that removes its limit and can raise your overall utilization. See how a payoff moves your number at wealthserene.com/tools/credit-score-simulator.