UPDATE: On April 9, the IRS solved the problem described, announcing that 2020 marketplace enrollees who received APTC do not have to file Form 8962.
The Internal Revenue Service announced today that taxpayers with excess APTC for 2020 are not required to file Form 8962, Premium Tax Credit, or report an excess advance Premium Tax Credit repayment on their 2020 Form 1040 or Form 1040-SR, Schedule 2, Line 2, when they file.
Those who filed prior to the passage of the American Rescue Plan Act and paid back excess APTC do not have to file an amended return; the IRS will reimburse them.
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In addition to increasing premium subsidies for 2021 and 2022 in the ACA marketplace, the American Rescue Plan Act signed into law by President Biden on March 11 provides an important benefit to 2020 marketplace enrollees. Section 9662 of ARPA stipulates that those enrollees who underestimated their income and so would normally have to pay back some the Advanced Premium Tax Credits (APTC) received will not have to pay back the excess APTC.
That includes people who estimated their incomes at below 400% of the Federal Poverty Level, the cap for APTC eligibility, but ended up with a declared income above that threshold. Normally, they would have to pay back all APTC received. This year, they owe nothing.
That is not a trivial benefit. According to IRS estimates,* in 2019 3.2 million tax filing households paid back a portion of the APTC they received in 2018, with paybacks totaling $4.4 billion, or about $1,375 per household. Estimating 1.7 enrollees per filing household** suggests payback of about $800 per enrollee. Similarly, the CBO report*** on the costs of ARPA estimated that APTC forgiveness for 2020 (when total enrollment was nearly identical to that of 2018) would cost $4.7 billion in 2021. (See Charles Gaba's detailed analysis here.)