"Married filing jointly" means you, as a married couple, file one tax return that lists all your combined income, deductions, and dependents. If that is your intention, you must file an amended return to add your information to the return he already filed.
If it is not your agreement to file jointly, then your other option is to file as "married filing separately." This almost always results in paying more tax because many deductions and credits are limited or disallowed. However, there are some circumstances where a married couple may want to keep their finances separate. In this case, you file a new original return as "married filing separately" listing only your own income and deductions, and your spouse will have to file an amended return to change from married filing jointly to filing separately. The deadline to change to married filing separately. is April 15 (extended to May 17 this year). If you wait longer, you will not be allowed to change to separate filing.
