filing single/married.

What is the name of your state? PA

my girlfriend and i lived together for over two years, we filed income taxes as 'single' for those years, and we have been married for over three years and are still filing 'single'. do we have a problem here? i says no, (i say her answer must be wrong).

[Snipes5]

If you are married, you can file Married Filing Jointly, or you can file Married Filing Separately.

If you are legally married, you cannot file Single.

Snipes

ok, I appreciate your answer but if we cannot file single while we are married, what can the IRS do regarding past and future single filings?

You should file corrected returns for all years, and be prepared to pay penalties and interest if more money is due. It's a heck of a lot cheaper to do this yourselves now than to wait for the IRS to discover your 'error'.

[Snipes5]

What can the IRS do? Require you pay them back whatever they decide is the correct amount that you owe them for the incorrectly filed years, plus penalties and interest.

What you should do is file amended returns for the years you were married. The options you have are Married Filing Separately, and Married Filing Jointly.

If it turns out that you owe, start paying, and pay them as much as you can, as quickly as you can.

They won't immediately come and arrest you or anything, but allowing this to drag on any longer than it has will only create more problems for you later.

Snipes

Filing single puts you in a higher tax rate than filing married joint, married /separate is a little better than single, but not much.
As the others have said, do amendments soon, you might actually have refunds for those years if the amendment lowers your tax liability, but if you owe pay quickly, interest and late penalties add up fast.