July 06, 2017 11:37 Updated Follow You can also make extra payments into your post-tax. This means your federal, state and Social Security taxes have already been withheld. Related articles Am I allowed to make voluntary contributions to my PERF plan? How do I make voluntary post-tax contributions to my Annuity Savings Account? How do I make voluntary pre-tax contributions to my Annuity Savings Account? How much can I match based on an employee’s additional (voluntary) contributions? How does a post-retirement rollover to an IRA or qualified plan at retirement affect my taxes?