If you earn too much to contribute to a Roth IRA directly, you have probably heard about the backdoor Roth.
The idea sounds simple: put money in a traditional IRA, convert it to Roth, and you're done.
In practice, a single overlooked form can turn a clean maneuver into a tax headache that follows you for years.
Here's how it actually works in plain terms.
The IRS phases out direct Roth contributions once your modified adjusted gross income crosses certain thresholds — for 2025, that's $150,000 to $165,000 for single filers and $236,000 to $246,000 for married couples filing jointly.
Above those numbers, you can't hand money straight to a Roth.
So people route it through a traditional IRA instead.
You make a non-deductible contribution to a traditional IRA, then convert it to a Roth.
If you also claim a deduction on that contribution, you've created a taxable event that can cost you more than the strategy saves.
You need to tell your tax software or preparer that this money was already taxed.
The second step is where the real damage happens.
When you file, you must report the conversion on Form 8606.
Skip it, and the IRS has no record that you already paid taxes on that money.
Down the road, a future withdrawal could be treated as fully taxable again.
That's double taxation on the same dollars, and it's entirely avoidable.
The "pro-rata rule" looks at all your traditional IRA balances as of December 31 of the conversion year.
If you have a big pre-tax IRA sitting somewhere — say, rolled over from an old 401(k) — the IRS doesn't let you convert only the after-tax dollars.
It calculates a ratio, and part of your conversion becomes taxable.
Many people discover this in April, not the previous December.
A common fix is to move that old pre-tax IRA into your current employer's 401(k) before doing the conversion, if the plan allows it.
That empties the traditional IRA balance out of the pro-rata calculation.
But check the plan's fees and investment options first, because a bad 401(k) can cost you more than the tax fix is worth.
One more thing people overlook: there's no income limit on conversions, but there is a five-year rule on converted amounts.
If you convert and then pull that money out too soon, you could owe a 10% penalty on part of it, even after age 59½ in some cases.
The backdoor Roth is still a legitimate, widely used strategy.
The people who get it right treat it like a two-part process: the contribution, then the paperwork.
The IRS doesn't send a reminder when Form 8606 is missing, and by the time it surfaces, you may be explaining yourself years later.
Our take: this maneuver is worth doing if you've maxed out other tax-advantaged accounts and you're willing to read the fine print.
Pay a tax pro for one hour the first time you try it, keep every Form 8606, and don't touch the converted money.
Final Thoughts
A little diligence now beats an audit letter later.