Legally separated but living together

[danifnp]

Legally separated in Colorado but still living together and sharing expenses. Can we still filed married jointly as we are not divorced or physically separated? Would common law apply? We wish to remain legally separated.

[NCperson]

@danifnp you are considered "unmarried" if you are legally separated. Therefore you can only file Single (assuming no children are involved). You can not file Married Filing Joint or Married Filing Separate. 

https://www.irs.gov/pub/irs-pdf/p501.pdf

see bottom right corner of Page 5

Unmarried persons. You are considered unmarried for the whole year if, on the last day of
your tax year, you are either:
• Unmarried, or
• Legally separated from your spouse under a divorce or separate maintenance decree. State law governs whether you are married or legally separated under a divorce or separate maintenance decree. 

you can also use this IRS app to get to the same answer: 

https://www.irs.gov/help/ita/what-is-my-filing-status