No, you will not have to pay back the premium tax credits you get if the Marketplace said you were eligible for premium tax credits and your income drops below 100 percent of the federal poverty level. In fact, you may get a refund. When you file your taxes, the credit you receive will be compared to the credit you should have received based on your actual income for the year. If your income goes down, you will get a refund for the difference between the two. Note however that if you intentionally provide inaccurate information about your income to the Marketplace, then you may have to pay back the premium tax credit.
If you apply again for premium tax credits, you may be asked to provide documents that prove you’ll have income above 100 percent of poverty in the year ahead in order to be found eligible for premium tax credits. (26 C.F.R. § 1.36B-2.)