There is no fixed or official rate for state tax withholding on a distribution from a retirement account. The amount that was withheld is whatever percentage you specified to the account trustee or custodian when you made the withdrawal. It has nothing to do with the tax rate that will apply to the distribution on your state tax return. The tax that was withheld on the 1099-R will be applied towards your total state tax obligation. It does not apply specifically to the retirement distribution.
