When you file as married filing jointly you report all of your income, including SSDI. When 1/2 of your SS benefit (either SSDI or regular SS) plus all of your other joint income is more than $32,000, then up to 85% of your SS benefit is taxable. There is nothing about SSDI that makes it non-taxable if your other income is above the limit. Further, you can not escape it being taxable by filing separately. If you are Married and live with your spouse, there is a special rule that says that if you file as married filing separately and you receive SS benefits (of any sort), then you must include your SS benefits in gross income when deciding whether to file, and 85% of your SS benefit becomes immediately taxable.
