Per IRS Publication 17 Your Federal Income Tax (For Individuals), page 27:
If your spouse died in 2021, you can use married filing jointly as your filing status for 2021 if you otherwise qualify to use that status. The year of death is the last year for which you can file jointly with your deceased spouse. See Married Filing Jointly, earlier.
You may be eligible to use qualifying widow(er) as your filing status for 2 years following the year your spouse died. For example, if your spouse died in 2020, and you haven't remarried, you may be able to use this filing status for 2021 and 2022.
This filing status entitles you to use joint return tax rates and the highest standard deduction amount (if you don’t itemize deductions). It doesn't entitle you to file a joint return.
Eligibility rules. You are eligible to file your 2021 return as a qualifying widow(er) if you meet all of the following tests.
As mentioned earlier, this filing status is available for only 2 years following the year your spouse died.
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the webpage or document at the time it is accessed.