Backdoor Roth explained

You can only contribute directly to a Roth IRA if your income is below certain limits (~$150k single, ~$236k married in 2025). But there's no income limit on converting money from a Traditional IRA to a Roth IRA. The 'backdoor Roth' exploits that gap: contribute to a Traditional IRA with after-tax dollars, then immediately convert it to Roth. Legal, explicit in the tax code, and endorsed by Congress in 2018.

The steps

1. Open a Traditional IRA and a Roth IRA at the same brokerage (if you don't already have them).
2. Contribute the annual max to the Traditional IRA with after-tax money. Do NOT deduct the contribution on your taxes.
3. Wait for the funds to clear — usually a day or two.
4. Convert the entire Traditional IRA balance to the Roth IRA. No tax is owed on the conversion because the contribution was after-tax.
5. Report the contribution and conversion on IRS Form 8606 at tax time.

The mega backdoor Roth

A related but more powerful strategy. Some 401(k) plans allow after-tax (non-Roth) contributions beyond the regular limit, plus in-service conversions to Roth. This can move up to $40k+/year into Roth-status money. Requires a specific plan feature — not all 401ks have it. If yours does, and you can afford it, it's extraordinarily powerful.

Why bother? The stakes over 25 years

A $7,000 annual backdoor Roth contribution feels small next to a high earner's income, but the compounding is not small. Run for 25 years at 7% growth, those contributions become roughly $475,000 — of which about $300,000 is earnings that will never be taxed. Had the same money sat in a taxable brokerage account instead, annual dividend taxes plus a final capital gains bill would claim somewhere in the neighborhood of $60,000-90,000 of it, depending on rates. For a married couple doing two backdoors a year, double everything. Fifteen minutes of clicks per year is well-paid work.

The pro-rata math, worked once

Common mistakes, ranked by expense

• Forgetting Form 8606. Without it, the IRS has no record that your contribution was after-tax and may treat the whole conversion as taxable. File it every year you contribute or convert — it can be filed standalone or amended in later.
• Converting with pre-tax IRA money still sitting somewhere (the pro-rata trap above). Check every old rollover IRA, SEP, and SIMPLE before starting.
• Deducting the traditional contribution by accident, then converting — creating taxable income that software will catch but you might not.
• Waiting months between contribution and conversion. Any growth in between is taxable on conversion. Small dollars, but converting within days keeps it clean.
• Missing that the limit is per person: each spouse can do their own backdoor, even a non-working spouse (via spousal contribution rules), doubling the household's Roth space.

Backdoor Roth vs. just investing in taxable

Some high earners skip the backdoor because the traditional IRA contribution isn't deductible anyway — 'what's the point of a nondeductible contribution?' The point is everything that happens afterward. In a taxable account, a 20% dividend-and-gains tax haircut compounds against you for decades and every rebalance is a taxable event. Inside the Roth, the same investments rebalance freely, distribute tax-free, and exit tax-free. The contribution was after-tax in both cases; only one of them ends the taxation there. The Roth also has no required minimum distributions during your lifetime, passes to heirs income-tax-free, and its contributions (not earnings) can be withdrawn anytime without penalty — making it a deeper emergency reserve than most people realize.

Is it legal? Is it going away?

The backdoor Roth sits in an odd reputational space: it sounds like a loophole, but Congress explicitly blessed it in the 2017 tax act's committee notes, and the IRS has processed millions of them without challenge. Legislative proposals to close it have appeared and died several times. The rational response: use it while it exists, keep clean Form 8606 records, and don't build a plan that collapses if the door closes — worst case, future contributions go to a taxable account and everything already converted stays Roth forever.

The bottom line

The backdoor Roth turns an income limit into a two-step formality: after-tax contribution, immediate conversion, Form 8606. Clear out pre-tax IRA balances first, do it early each year, and repeat for each spouse. It's the rare high-earner tax strategy that requires no lawyers, no fees, and no risk — just knowing the door exists.