Calculate your Solo 401(k)
Your 2025 contribution limits
Solo 401(k) vs SEP-IRA at your income
Why Solo 401(k) can beat SEP-IRA at lower incomes
Both plans have the same $69,000 overall limit, but they get there differently. A SEP-IRA allows only employer contributions (up to 25% of net compensation). A Solo 401(k) allows both employee contributions (up to $23,500 in 2025) AND employer contributions (up to 25% of net compensation).
At lower income levels, the employee contribution portion of a Solo 401(k) lets you shelter far more income than a SEP-IRA. At higher incomes, the two plans converge. Use this calculator to see which plan lets you contribute more at your specific income level.
Traditional vs Roth
Employee contributions to a Solo 401(k) can be either traditional (pre-tax) or Roth (after-tax). Employer contributions must be traditional. For most gig workers in their peak earning years, traditional contributions make more sense — you deduct now when your tax rate is higher, and pay taxes in retirement when your rate may be lower.
Setup requirements
A Solo 401(k) must be established by December 31 of the tax year you want to contribute for. You can make contributions until your tax filing deadline (including extensions). Most major brokerages offer Solo 401(k) plans — Fidelity, Schwab, and Vanguard all have strong options with no fees.