If during a tax year, my spouse was a non-resident with no SSN or ITIN, what do I put in the field asking for their SSN/ITIN?

[satterthg]

My spouse currently is a permanent resident and has a social security number. However, I am filing previous years in which my spouse had neither a SSN nor an ITIN.

For said years, what do I enter in the field asking for her SSN/ITIN? I have seen advice saying that one should leave it blank, fill it with 0's, or write "NRA". Thus, I am still thoroughly stumped. Any help would be very much appreciated!

[satterthg]

I should also add that I have contacted the IRS directly, and they also did not know what to do in this situation.

[Leonard]

You have to enter either an SSN or ITIN the field cannot be blank be filled with 0's or NRA 

If your spouse is a nonresident alien and you file a joint or separate return, your spouse must have either a Social Security Number (SSN) or an Individual Taxpayer Identification Number (ITIN). ... If your spouse is not eligible to get an SSN, he or she can file Form W-7 with the IRS to apply for an ITIN.

[satterthg]

My spouse currently has a SSN, and it is not permissible to have both a SSN and an ITIN. The problem is during the years for which I wish to file, my spouse did not have one. She no longer qualifies, however for an ITIN.

It seems like a very specific, odd situation.

[Leonard]

If your spouse has a SSN then use the SSN on your tax return

[satterthg]

Even on a return for the year 2015, a year during which she had no SSN?