You can file Form 8379 with your joint return or amended joint return (Form 1040-X), or you can file it afterwards by itself. File Form 8379 with Form 1040-X only if you are amending your original return to claim a joint refund.
https://www.irs.gov/instructions/i8379#:~:text=You%20can%20file%20Form%208379,to%20claim%20a%20joint....
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
