What is the 'backdoor Roth IRA' strategy primarily used for?

For 2025, single filers with modified adjusted gross income above $165,000 and married filers above $246,000 cannot contribute directly to a Roth IRA. The backdoor Roth involves making a nondeductible (after-tax) contribution to a Traditional IRA and then promptly converting it to a Roth IRA. The pro-rata rule can create tax complications if you hold other pre-tax IRA balances, so many strategists first roll those into an employer 401(k) before executing the backdoor.