The Solo Ledger
Freelancers, contractors and business owners answer one question first: which retirement account fits the way you earn. Below is the preview we keep identical to the full matrix, criterion by criterion.
Tax year 2025 figures. Every limit carries a superscript marker that resolves to its source in the matrix below.
| Criterion | Solo 401(k) | SEP IRA | Traditional IRA | Roth IRA |
|---|---|---|---|---|
| Employee deferral1 | $23,500 | Not allowed | $7,000 | $7,000 |
| Employer contribution | Up to 25% of compensation | Up to 25% of compensation | None | None |
| Tax treatment | Pre-tax or Roth | Pre-tax only | Pre-tax, deductible | After-tax |
| Plan established by | Dec 31 of the tax year | Tax filing deadline | Not required | Not required |
| Loans from the plan | Allowed | Not allowed | Not allowed | Not allowed |
1 Source: IRS tax year 2025 contribution limits, listed in full in the master matrix.
01 / OPTION SHELF
Which one lets you put the most away this year, and who is allowed to open it.
Tax year 2025 figures1. Limits and phase-outs are adjusted most years, so confirm the current amount before you file.
Open the full comparison matrix03 / Matrix
Five accounts in fixed row and column order. Figures are tax year 2025 and each one carries a footnote.
| Criterion | Solo 401(k) | SEP IRA | SIMPLE IRA | Traditional IRA | Roth IRA |
|---|---|---|---|---|---|
| Employee deferral | $23,5002 | None | $16,5003 | $7,0004 | $7,0004 |
| Employer contribution | Up to 25% of net earnings | Up to 25% of net earnings | 3% match or 2% flat | None | None |
| Total annual cap | $70,0005 | $70,0005 | $17,6003 | $7,0004 | $7,0004 |
| Tax treatment | Pre-tax deferral, Roth option | Pre-tax only | Pre-tax, Roth option | Deductible now, taxed later | After-tax, tax-free growth |
| Setup deadline | Dec 31 for deferrals6 | Tax filing deadline | Oct 1 for a new plan6 | Open any time | Open any time |
| Loans permitted | Yes, if the plan allows | No | No | No | No |
| Best for | High earners who want the largest cap | Owners who want minimal paperwork | Firms with a handful of staff | Simple pre-tax savings | Savers expecting a higher future bracket |
04 / Deadlines
The paperwork and the money move on separate calendars. Missing either one costs a deduction.
Read the ledger by column. The date tells you when something must happen, the description tells you what happens, and the tag tells you whether that date creates the plan or funds it. Solo 401(k) plan adoption is the only line that cannot be moved by an extension.
Verify the current tax year before you act. Dates shift when a deadline lands on a weekend or federal holiday, and income limits are revised annually. Check IRS Publication 560 and the current Form 1040-ES for the year you are filing.
Section 05
Method before conclusions.
Four rules govern every account page and the master matrix. They are here so you can audit the work instead of trusting it.
A limit, threshold, or date never appears alone. Each one is stamped with the year it applies to and a superscript marker that resolves to the source entry at the bottom of the page.
Solo 401(k), SEP IRA, Traditional IRA, Roth IRA, SIMPLE IRA. The same sequence, the same criteria, everywhere they appear, so two pages can be read side by side.
That is where these accounts actually diverge, so it is the first row compared. How the employer side is calculated, whether a uniform percentage applies to every eligible employee, and when it vests.
Each account closes with three to five honest places it struggles. An account page without that section does not ship.
No custodian, brokerage, or administrator pays for a position, a row order, or a sentence. If that ever changes, the page will say so above the fold.
We hold no accounts on your behalf, take no commissions, and cannot open anything for you. This is educational comparison, not advice on your situation.
Every deadline and limit is tested against a single reader profile: a self-employed professional filing as an individual. If a rule does not hold for how you file, write to us and it gets corrected.
Read the method, then read the numbers. Open the master matrix or review our editorial standards and corrections log.
05 / Glossary
Penalties, rollovers, and the side-business questions readers send most often. Every figure carries a tax year and a source.
A 10% additional tax on the taxable amount sits on top of ordinary income tax, with narrow exceptions. A SIMPLE IRA inside its first two years carries 25% instead.1
Usually yes, when the plan document permits incoming rollovers. A direct trustee-to-trustee transfer is not taxable, and Roth balances land in a designated Roth account.2
The Solo 401(k) covers self-employment income only, and salary deferrals at your day job share the same annual employee limit. A SEP IRA also fits when the side work has no employees other than you and your spouse.3
Two different deadlines. The plan has to be adopted by December 31 of the tax year, while employer funding can follow the extended filing deadline. Employee deferrals still need to come out of pay during the year.4
Best for: a Solo 401(k) when you want the largest employee deferral, a SEP IRA when you want the least paperwork. Compare all five accounts Estimate your contribution room