When you are married and have a spouse that receives Social Security disability (SSDI)* you are NOT required to file as married filing jointly (MFJ). But, you still should.
You may be thinking that filing Married Filing Separately (MFS) is going to save you money, because you won't have to add your spouse’s income to your return. That thinking is usually wrong. There is a special rule that says SS becomes taxable at zero ($0) other income when Filing as MFS. The doubled standard deduction will usually wipe out all the spouse’s income, on a joint return. But you will still get to use the lower joint filing rates.
Before making a decision to file as MFS, you should run test returns and compare. You can use this tool: https://turbotax.intuit.com/tax-tools/calculators/taxcaster/?s=1
*Supplemental Security Income (SSI) is tax free welfare and not the same as Social Security Disability Income (SSDI), even though SSI is administered by the Social Security Administration (SSA). If you spouse does have SSI (rather than SSDI), that is all the more reason to file MFJ, because SSI is not reportable, at all.
