What's the Difference Between Pre-Tax and After-Tax Retirement Contributions?

When contributing to a retirement account, whether your contribution is pre-tax or after-tax determines when you pay taxes on the money. Pre-tax contributions — like traditional 401(k) or traditional IRA contributions — reduce your taxable income in the year you contribute, giving you an immediate tax break, but you'll pay income tax on every dollar you withdraw in retirement. After-tax contributions — like Roth 401(k) or Roth IRA contributions — don't reduce your taxes now, but the money grows tax-free and qualified withdrawals in retirement are completely tax-free. Some 401(k) plans allow a third type called after-tax non-Roth contributions, which can then be converted to Roth funds in what's called a mega backdoor Roth — a strategy for high earners who want to maximize tax-free retirement savings. The right mix of pre-tax and after-tax contributions depends on your current tax rate compared to your expected tax rate in retirement.