As a general matter, no, it's not possible to change a joint return to a separate return after the original due date for the return in question. With all due respect, it sounds like you may be out of your depth; I would strongly urge you to at least consult with a competent local tax professional before you go ahead and do anything on your own.
My answer does not constitute legal advice and may not be relied upon by anyone for any purpose and does not constitute an attorney/client relationship or an offer to form such a relationship. This disclaimer is intended to be fully compliant with the requirements of Treasury Department Circular 230 and the terms thereof are fully incorporated by reference. If you wish to consult with me please contact me at dwatchley@newyorktaxcounsel or visit my website at www.newyorktaxcounsel.com
Use form 1040X and adjust the deduction figures on the 1040 and respective forms.
Evan A. Nielsen is licensed to practice law in California and handles federal tax matters throughout the U.S. The information provided here is for educational purposes only and is not intended as legal advice for a particular matter. This response does not create any attorney-client relationship with the author. For specific advice about your particular situation, please consult an attorney.
As a rule, you may only change from MFS to MFJ. There are very few reasons to change from MFJ to MFS, which the IRS does not allow anyway (as a rule). If you are willing to pay a CPA, have the CPA do your next tax return so it will be done right. Your credit cards, banks, power company.....all have your SSN, go giving it to a CPA or a Tax Attorney is safer because of the legal responsibilities professionals must follow to protect you.