Each account is a card. The fields below define how the engine taxes growth, where it can deposit surplus cash, and how it draws money down in retirement.

Fields

• Account Name - used in Proof tables and events.
• Account Type - controls tax and withdrawal handling.
• Allocation (pie icon) - dollar mix by asset class within the account.
• Fees (%) - annual drag applied to account growth.
• Initial Cost Basis (Brokerage) - the dollar amount of your brokerage balance that is original contributions, not gains.
• Person - ownership mapping for timing and tax behavior.
• Balance - total account value used to scale allocation amounts.
• HSA Coverage (HSA only) - Self or Family for contribution logic.

Solo 401k (self-employed retirement plan)

A Solo 401(k) (also called one-participant 401(k), Individual 401(k), Uni-K, or Solo-K) is a 401(k) designed for self-employed people with no full-time non-spouse employees. FIREproof supports both Traditional Solo 401k and Roth Solo 401k as account types.

Who is eligible

• Sole proprietors reporting income on Schedule C.
• Single-member LLCs taxed as sole proprietorships.
• S-corp owner-employees who pay themselves W-2 wages.
• A spouse who earns income from the business may also participate; any other full-time non-spouse employee disqualifies the plan.

The two-hat contribution structure

Because you are both the employee and the employer, you contribute in two capacities. The two limits stack, up to the §415(c) per-account cap.

• Employee elective deferral (§402(g)): a flat dollar limit that is shared across every 401(k)-style account you own (W-2 401k, 403b, TSP, and the Solo 401k all draw from the same bucket).
• Employer non-elective contribution: a percentage of net self-employment earnings. The percentage depends on entity type.

2025 limits

The 60-63 enhanced catch-up is the SECURE 2.0 "super catch-up". It applies in the calendar years you are 60, 61, 62, or 63, and snaps back to the standard 50+ catch-up at age 64.

Employer non-elective contribution caps depend on entity type:

• Schedule C / sole prop / single-member LLC: roughly 20% of net self-employment earnings after deducting one-half of self-employment tax. (The on-paper 25% rate gets reduced to ~20% once the contribution itself is netted out of the base.)
• S-corp owner-employee: 25% of W-2 wages from the S-corp.

Traditional vs Roth Solo 401(k)

• Traditional Solo 401k: contributions reduce income tax in the year contributed. Note that the non-elective employer contribution reduces income tax only. It does not reduce self-employment (SE) tax, because SE tax is computed on net earnings before the retirement contribution deduction. Withdrawals are taxed as ordinary income.
• Roth Solo 401k: contributions are made post-tax. Under SECURE 2.0 §604, the employer non-elective portion can also be designated as Roth (post-tax), not just the employee deferral. Qualified withdrawals are tax-free.

Required minimum distributions

• Traditional Solo 401k: RMDs apply at age 73 (rising to 75 in 2033 under SECURE 2.0).
• Roth Solo 401k: no RMDs during the owner's lifetime (SECURE 2.0 §325, effective 2024). This mirrors the long-standing Roth IRA treatment and removes the historical "roll Roth 401(k) to Roth IRA to escape RMDs" workaround.