If I was taxed for my military severance pay can I get the taxed part back in I have a military disability?

If you were discharged due to disability or injury and tax was withheld from your severance pay, the Department of Defense will notify you with directions to amend the income tax return.  

If you became disabled after you were discharged, then you were not wrongly taxed on the severance pay.  Your military disability payments are never added to your income tax and you never pay tax on them.

See https://www.irs.gov/individuals/military/special-tax-considerations-for-veterans for guidance. Note that you will have to mail the amended return. If this is for 2021 taxes, then *you* can adjust the 1099-R yourself, ***AND*** then you will still have to mail the return since you have to include the VA paperwork with the return. Processing will take longer since it has to be done by hand.