"The employee contribution limit for one-participant 401(k) plans in 2024 is $23,000. The limit for employer contributions is up to 25% of compensation. Because I am self-employed, I can contribute both as the employer and the employee."
It's 20% of net earnings, not 25%. For the self-employed, a special calculation reduces the 25% base rate to 20% because the employer contribution effectively reduces net earnings. Marking the Maximize box in TurboTax for an individual 401(k) contribution will cause TurboTax to calculate the maximum permissible contribution (assuming that you have not also made elective deferrals to a different employer's plan in the same year, in which case you would have to use the Maximize function for a SEP contribution to calculate only the employer contribution).
