If you have health insurance through the marketplace, the government helps pay your premiums. They do this by sending amounts directly to the insurance company.
Then, at the end of the year, the amount that you should have received in this assistance is reconciled, because this assistance is called the Premium Tax Credit (PTC), and the amount the you should receive (i.e., go to the insurance company on your behalf) is based on your estimated income for the year. When you have major life changes, like having a kid or getting married or going on Medicare, you should have called the marketplace to report this so they could adjust the amount of PTC that you were receiving.
The amount of PTC is calculated on form 8962. Check this form to see if you were required to return some of the PTC (this often increases tax due).
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