If we need to amend our filing status from single to married filing or separate, do both of us need to amend the returns, or do we just amend one?

[Critter-3]

If you each filed SINGLE  incorrectly because you were married as of 12/31/22  and the single filing status was taken in error  beause it  was not allowed  then you will either :

1)  amend ONE of your single returns  to switch to married filing JOINTLY

OR 

2) amend BOTH single returns to switch to married filing SEPARATELY on both returns

[VolvoGirl]

Well one of you need to amend to MFS.  Probably the primary person.  Then the other spouse has to file a separate return.  You will both have to mail the returns the returns this year.   

Unless you want to file a joint return.  Then amend the Single return to Joint and add the other spouse to it.