I am married filing separately and I do not have access to find out my wife's SSN. It is required to put in so not sure what to do.

If you have access to a prior year tax return where you filed joint, you can get the spouses SSN from there. Otherwise, you'll need to contact your spouse since you need the SSN in order to file the tax return.

The IRS requires this of a couple filing separately, because if one of you itemized deductions, then you are both required to itemize; even if the itemized deductions for one of you is ZERO.

Likewise if one of you takes the standard deduction, then you must both take the standard deduction; even if the itemized deductions would be higher for one of you.

The IRS requires the spouses SSN so they can cross check this.

don't know your situation, so if she doesn't provide it and you can't get it you will have to mail in your return. attach a note indicating spouse would not provide their SSN.