I think this is a single person, a widow, FS is describing. The federal tax on Social Security varies, depending on total taxable income. State tax also varies. Some states do not tax Social Security and some do not tax pension income.
Medicare Part B premiums will be deducted from Social Security, and the recipient will automatically be signed up IIRC. There are a lot of pitfalls involved in not signing up for Medicare timely and in the current environment, continuous insurance coverage will be critical.
Best to run the numbers through one of the tax programs, including a state return.