If your income for 2023 turns out to be greater than the amount you estimated when you sign up, you may have to repay some or all of the excess credit.  For example, say you estimated at sign up that your 2023 income would be 350% of the poverty level, and you receive advanced premium tax credit of $4,300 based on that income.  But, when you file your 2023 return, your actual income turns out to be 410% FPL and you would only be eligible for a $3,100 tax credit based on that income.  In this case you might have to repay the excess credit ($1,200) when you file your 2023 return.  

If you experience a change in income during the year, you can log into your marketplace account, update your information, and reduce the monthly premium tax credit for the remainder of the year in order to minimize any excess credit that might need to be repaid.