The stimulus payments now hitting bank accounts are designed to help most Americans weather the economic downturn caused by the coronavirus pandemic. But some people are excluded from the payments, including some U.S. citizens who are married to immigrants.

The government's $2.2 trillion economic relief package excludes several groups from the payments, which amount to $2,400 for married couples earning less than $150,000. Among those are nonresident aliens — meaning immigrants without Green Cards. But the IRS now says that American citizens who are married to immigrants without Social Security numbers are also blocked from receiving the payments.

About 1.2 million immigrants are married to U.S. citizens, according to the Migration Policy Institute. The IRS says that only married couples in which both partners have valid Social Security numbers will receive stimulus checks. That effectively excludes legal immigrants who use an Individual Taxpayer Identification Number to file taxes.

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It could also prove an unwelcome surprise for some U.S. taxpayers who were counting on the federal payments to help them through the economic downturn.

"Several Iowans who are taxpayers and U.S. citizens have contacted me," wrote Iowa state Senator Claire Celsi on Twitter. "They're not receiving their stimulus checks if the[y] are married to immigrants."

The exclusion also affects children, according to the Los Angeles Times, which earlier reported about the impact on U.S. citizens who are married to immigrants.

Taxpayers who are citizens and file separately from their immigrant spouses who lack a Social Security number will receive the half of the payment, according to the IRS. That could give some couples a chance to file their taxes separately, given that the 2019 filing deadline has been pushed back to July 15. However, many taxpayers have already filed their returns for 2019.

The issue won't impact members of the U.S. military, the IRS says. If either spouse is a member of the Armed Forces at any time during the tax year, only one of them is required to have a valid Social Security number, according to the agency.

The treatment of immigrants under the stimulus bill has struck some policy experts as hurtful. After all, legal immigrants pay taxes and otherwise contribute to the economy, and they, too, have been swept into the economic freefall caused by the coronavirus.

The Coronavirus Aid, Relief and Economic Security, or CARES, Act states that immigrants are excluded from the stimulus payments, with one exception: Those who hold a Green Card. Otherwise, immigrants aren't eligible for the payments even though legal immigrants who are in the U.S. on work visas also pay taxes. There were 2.3 million foreign nationals on temporary visas in 2016, according to the Migration Policy Institute.

Other groups of people are also excluded from the stimulus payments. That includes adults who were claimed as dependents on another person's tax return, which applies to many college students as well as disabled adults. Young people who are 17 or older also are ineligible to receive the $500 stimulus payment for children.

Lastly, high-income Americans are also barred from receiving the payments. The $1,200 payment for single taxpayers phases out at income above $99,000, while the $2,400 payment for married couples disappears at income over $198,000.