My mother-in-law claimed my husband on her taxes We still live with them but we pay way more than half of our expenses. What can we do? When we go to file it says we cant

[DoninGA · Accepted solution]

You cannot e-file your tax return because another tax return with his Social Security number has been accepted by the IRS with him as a dependent.  You will have to print and mail your tax return.  Complete your tax return as you would have without the MIL claiming him as a dependent.  Print, sign and date the tax return.  Include with the return all W-2's and Form 1099's which have taxes withheld.  If you have a tax refund the IRS will pay the refund.

See this TurboTax support FAQ for printing a tax return for mailing when using the online editions - https://ttlc.intuit.com/questions/1944348-how-do-i-print-and-mail-my-return-in-turbotax-online

After a few months the IRS will contact all parties to investigate why more than one tax return was filed with the same personal exemption.  The loser of the investigation has to pay back any refund associated with the personal exemption plus penalties and interest.

Note - If your spouse is over the age of 18, not a full time student and had gross income of $4,050 or more then no one can claim him as a dependent.  You should be filing your tax return as Married Filing Jointly so both of your personal exemptions are on your joint tax return.

[Hal_Al]

For a full discussion on whether a parent can claim a married child, see <a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/2938663-can-i-claim-my-daughter-who-got-married-on-december-19th-2...>
The home the parent provides is  large part of the support calculation. The IRS has a worksheet that can be used to help with the support calculation. See: <a rel="nofollow" target="_blank" href="http://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf"...>