Backdoor Roth Wizard

The IRS doesn't let you cherry-pick which dollars convert. When you do a Backdoor Roth, the IRS looks at all your pre-tax IRA balances (Traditional + SEP + SIMPLE) plus the non-deductible contribution you just made, and treats your conversion as a proportional slice of that total.

Example: you have $93K in a SEP IRA from a side gig and you contribute $7K non-deductible to a Traditional IRA, then convert $7K to Roth. The IRS sees: total IRA = $100K, of which $93K (93%) is pre-tax. Your $7K conversion is therefore 93% taxable — a $6,510 taxable event at your marginal rate. At 32%, that's a ~$2,083 tax bill on what you thought was a tax-free move.

The avoidance strategies mostly involve getting the pre-tax IRA balance to $0 before doing the backdoor: roll it into your current 401(k) (if your plan accepts incoming rollovers), or if you're self-employed, into a Solo 401(k). Only AFTER that move do you start the backdoor. The math becomes clean.

Most calculators surface the contribution limit and stop there. Sagery surfaces the pro-rata percentage so you know whether this strategy will cost you money or save you money — before you initiate the conversion.