Self-Employed · Freelancers · 1099

Illinois Solo 401(k) Calculator 2026

Your exact contribution limit and combined federal + Illinois state tax savings. Free, no sign-up.

Illinois state tax

5.0% State Rate

2026 max contribution

$70,000

Est. total savings*

$11,319

Deadline to open

Dec 31, 2026

*Based on $42,000 contribution at 22% federal + 5.0% state rate

Illinois tax note: Illinois levies a 5.0% state income tax. Your Solo 401(k) contributions reduce both your federal and Illinois taxable income, boosting your total tax savings beyond the federal benefit alone.

Your situation

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✦ Import from document

Paste an offer letter, 1099, contract, or any document with income details — Claude will fill the fields for you.

Affects catch-up contribution limits (age 50+, 60–63 enhanced)

From Schedule C line 31, or your best estimate if mid-year

Enter 0 if you have no day job. Affects IRA deductibility and total 401(k) room.

An HDHP (high-deductible plan) unlocks HSA contributions — the only triple-tax-advantaged account

Traditional IRA, SEP-IRA, or SIMPLE IRA balances. Affects backdoor Roth eligibility.

We never store your inputs. All calculations happen on our server.

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Your 2026 retirement plan

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Solo 401(k) Tax Savings in Illinois

Illinois levies a 5.0% state income tax. Your Solo 401(k) contributions reduce both your federal and Illinois taxable income, boosting your total tax savings beyond the federal benefit alone.

At 5.0% Illinois income tax plus 22% federal, a $42,000 Solo 401(k) contribution saves approximately $11,319 in combined taxes — $9,240 federal and $2,079 state. That's a 27.0% combined tax savings rate on every dollar contributed.

How to open a Solo 401(k) as a Illinois freelancer

  1. Get an EIN — free at IRS.gov, takes 5 minutes. Required even as a sole proprietor.
  2. Choose a provider — Fidelity, Schwab, and Vanguard offer free Solo 401(k) plans with no annual fees.
  3. Open by December 31 — the account must exist before year-end for contributions to count for that tax year.
  4. Fund by your filing deadline — April 15, 2027, or October 15 with an extension.

Frequently Asked Questions

How much can a self-employed Illinois resident contribute in 2026?

The 2026 Solo 401(k) limit is $70,000 ($77,500 with catch-up for those 50+). Your exact maximum depends on your net self-employment income after the SE tax deduction. Use the calculator above for your specific number.

Does Illinois tax Solo 401(k) contributions?

Illinois follows the federal treatment. Traditional (pre-tax) contributions reduce your Illinois taxable income at the 5.0% state rate, providing savings at both the federal and state level.

Solo 401(k) vs. SEP-IRA — which is better for Illinois freelancers?

For most Illinois self-employed professionals earning under $280,000, a Solo 401(k) allows larger contributions than a SEP-IRA — especially at income under $120,000. Both receive the same Illinois state tax treatment on contributions.

When is the Solo 401(k) deadline for Illinois residents?

The account must be open by December 31, 2026. Employee deferrals are elected by year-end. Employer contributions can be made up to your tax filing deadline — April 15, 2027, or October 15 with an extension.

Solo 401(k) guides by state

All states →IndianaMissouriIowa

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