There is a limitation of the repayment of the premium tax credit if your household income is less than 400% of the federal poverty level. If your household income is more than 400% of the federal poverty level, there is no limit to the repayment.
Please read this IRS document for more information:
https://www.irs.gov/affordable-care-act/individuals-and-families/four-things-to-know-about-advance-payments-of-the-premium-tax-credit