Yes, your unused Clay credits will roll over to the next month. For monthly subscriptions, unused credits accumulate in your account up to a maximum of 2x your plan's monthly credit limit.For example, if you're on a pro plan with 50,000 credits per month, you can accumulate up to 100,000 credits.If you have an annual subscription, the system works differently - you receive all your credits upfront and can use them however and whenever you'd like throughout the year.
Sources:Clay Credits Overview - Clay UniversityFAQ | Clay.comCredit Rollover Monthly vs. Annual Plans