If married in Mexico, do you have to file as married when filing taxes?

Question

I'm attempting to do my mother-in-law's taxes...she was born in Mexico and got married there to another Mexican about 30 years ago...when filing for taxes here does she have to file as married? They never married here or anything. I was just running the numbers and she would get more if filing as single but I don't know if that's allowed...

She is now a citizen but he is not. He's not legal I guess you could say.

Answer 1

You don't provide enough information. Are either of them US Citizens or resident aliens, do they have a SSN/ITIN number.
Normally if you are married you claim either Married filing joint or Married Filing Separately. It doesn't matter what country they were married in. Both need to have SSN or ITIN number to be able to file a return. If they don't have at least an ITIN number then an application for it must be included with the return

updated
she is married and can File jointly but he needs an ITIN number to do so. Include a W7 with the return.
Go to www.irs.gov and type in form W7 to access the form needed, you send your return with the form W7 and the required documentation requested to the Philadelphia address in the instructions for the W7, they will process the W7 issue him an ITIN number and then process the tax return.
for more information please call the Internal Revenue Service
1-800-829-1040 www.irs.gov

Answer 2

She can't file legally as single. If the marriage was legal when and where it took place, then she's married.

Answer 3

Yes