The initial guidance, issued by the I.R.S. on Monday, drew criticism from lawmakers in both parties. Representative Richard E. Neal, Democrat of Massachusetts and chairman of the House Ways and Means Committee, urged Treasury Secretary Steven Mnuchin and Social Security officials to find a solution that did not involve filing an additional return. Senator Tom Cotton, Republican of Arkansas, wrote on Twitter that he was “extremely disappointed” in the I.R.S.

The reversal should allow Social Security recipients to avoid filing an unexpected return, but the same cannot be said for many others who do not normally have to file.

The I.R.S. guidance acknowledged the potential complexity for low-income Americans, and the agency said it would “soon” offer instructions on its website for filing a 2019 tax return that contained “simple, but necessary, information including their filing status, number of dependents and direct deposit bank account information.”

Filing even the simplest of returns could pose challenges during a pandemic. The I.R.S. does have a free filing site, but those who lack internet access could be unable to use it because nonprofits, libraries and other places are closed. Low-income filers, however, will have until the end of the year to file and still get their stimulus payments.

The decision to require more people to file returns puzzled policy experts, who said the government had the ability to crosscheck various databases to make sure it reached everyone who was eligible, including those who would have the greatest need.

“The matching part may take longer, and it’s legitimate for them to say that one group will get payments faster and one group will be slower,” said Ms. Parrott, who worked in the federal Office of Management and Budget during the Obama administration. “But to throw up their hands and say they can’t do it? They have the capacity to do it, and I think they need the leadership to say that they are going to get this done.”

There will be an extra layer of difficulty for people who don’t normally file a return and lack a standard checking account.