High earners are often told they make too much to contribute to a Roth IRA, and that is true of the front door. The back door is a legal, well-established path to the same place, and it is simple in concept and surprisingly easy to execute wrong.
A Roth IRA has an income limit for direct contributions, above which you are shut out of the front door. But there is no income limit on converting a traditional IRA to a Roth. The backdoor Roth is just those two facts used in sequence: contribute to a traditional IRA, which anyone can do, then convert it to a Roth. The result is money in a Roth that your income would otherwise have blocked.
The step that trips people is the pro-rata rule. If you hold other pre-tax IRA money, the IRS does not let you convert only the after-tax dollars; the conversion is taxed proportionally across all your IRA balances, which can turn a supposedly tax-free maneuver into a taxable surprise. Anyone with an existing traditional, SEP, or SIMPLE IRA needs to understand this before executing, because the fix, and whether one exists, depends on the specifics. This is exactly where a conversation with your CPA earns its keep.
For those with the right kind of workplace plan, a mega backdoor Roth extends the same idea to after-tax 401(k) contributions, moving a much larger amount into Roth treatment. It depends entirely on plan features that many plans do not offer, so the first question is whether your plan even allows it. As with the standard version, the mechanics are simple and the execution details are where the value, or the mistake, lives. This is general information, not personalized tax or investment advice; confirm current limits and your own situation with your tax advisor.
A legal door most people miss. Just do not slam it on the pro-rata rule.