Confused by the mention of "part- time"----do you mean one of you has a part-time job in addition to the Social Security benefits you are receiving? If you need to file a tax return, filing a joint return is almost always better. If you file separate returns you will pay tax on almost all of your Social Security. It is not clear whether you even need to file. If your ONLY income is Social Security, you do not need to file a tax return unless you have a 1095A for marketplace health insurance.
If you have other income in addition to the Social Security, you may need to file.
You need to file a federal return if half your Social Security plus your other income is
Single or Head of Household $25,000
Married Filing Jointly $32,000
Married Filing Separately $0
Who has to file?
http://www.irs.gov/uac/Do-I-Need-to-File-a-Tax-Return%3F
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**