Yes you can amend to change from MFJ to MFS up until 4/18/2021 however make sure that if one person is claiming the deductions on the Sch A then BOTH must use the Sch A even if the other spouse has little to no deductions to take. One cannot itemize and the other take the standard deduction ... both parties MUST use the same deduction.
AND if you got the advance CTC payments the you must each enter the portion you got in advance as reported on the individual 6419 letters that you were sent on the separate returns ... all of the advance cannot go on just one return.
