income will only come from federal pension and SS benefits, is it advantageous to continue voluntary tax deductions?
The key word is "withholding." You want to have enough taxes withheld from the SS benefit, pension, or both, to cover most of your tax bill. The alternative is to make quarterly estimated payments. This is ok, but if you miss one, you can be assessed an under-payment penalty even if you pay in full when you file your return. If you have too much withheld, it comes back as a tax refund, of course.
Withholding should account for the tax you anticipate paying. It makes no difference where the withholding comes from.
The key word is "withholding." You want to have enough taxes withheld from the SS benefit, pension, or both, to cover most of your tax bill. The alternative is to make quarterly estimated payments. This is ok, but if you miss one, you can be assessed an under-payment penalty even if you pay in full when you file your return. If you have too much withheld, it comes back as a tax refund, of course.