Illinois TRS Taxes: What's Taxed, What's Not, and How to Set Withholding

The short version: exempt in Illinois, taxable federally

These are two separate tax systems asking two separate questions, and TRS benefits get a different answer from each. Illinois asks whether retirement income should be part of your state taxable base, and the answer for TRS, like nearly every other pension and retirement account, is no — it's excluded entirely. The IRS asks whether the money you're receiving now was already taxed before it went into the plan, and for most TRS members the answer is no, because the bulk of your career contributions went in pre-tax, so the benefit comes out as ordinary taxable income at the federal level.

That combination — full state exemption, near-full federal taxability — is common for public pensions generally, but it's easy to assume incorrectly in either direction: assuming Illinois taxes it because the IRS does, or assuming the IRS treats it like tax-free municipal income because Illinois does. Neither assumption is right.

Where the Illinois exemption actually comes from

The Illinois Department of Revenue's own guidance on Form IL-1040 subtractions specifically names "Illinois Teacher's Retirement" as an example of the retirement income you subtract on Line 5 of your Illinois return before it counts as state taxable income. This isn't a TRS-specific carve-out — Illinois exempts essentially all qualifying retirement income (pensions, 401(k)/403(b)/457 distributions, IRA withdrawals, and Social Security) the same way — but it does mean a TRS retiree living in Illinois pays no state income tax on the benefit itself, full stop, regardless of how large the pension is.

If you also have other income sources in retirement — a spouse's W-2 wages, rental income, taxable investment gains — those remain subject to Illinois tax as usual. The exemption applies specifically to the qualifying retirement income line, not to your household's total income.

Why the IRS treats it so differently

TRS is funded by three sources: your own payroll contributions (9.0% of creditable earnings, mostly pre-tax under Illinois's pension pickup arrangement), investment earnings on the fund, and state appropriations. Only the narrow slice of your contributions that was ever after-tax money is treated as your "cost basis" and returned to you tax-free; everything else — the pre-tax contribution portion, the investment growth, and the state's funding share — comes out as ordinary federal income, taxed at your marginal rate the same as a paycheck would be.

Because most TRS members' career contributions were pre-tax, the after-tax cost-basis slice is usually small relative to a full career's benefit, which is why the practical rule of thumb — "assume it's almost entirely federally taxable" — holds for most retirees. Your own 1099-R shows the exact split for your situation rather than a generic percentage.

Reading your 1099-R

The Illinois Office of the Comptroller (not TRS directly) issues your Form 1099-R by January 31 each year for the prior calendar year's benefit payments. Box 1 shows the total gross benefit you received; Box 2a shows the taxable amount for federal purposes; Box 5 shows the non-taxable portion — the after-tax cost-basis recovery described above, not a health-insurance premium figure despite sometimes being confused with one. If a form doesn't arrive by mid-February, request a duplicate through your MyTRSIL account rather than assuming it was never sent.

Setting your federal withholding with Form W-4P

TRS withholds federal income tax from your monthly benefit based on the election on file from your Form W-4P, the IRS's withholding certificate for periodic pension payments. If you've never filed one, or filed it years ago under the pre-2022 allowance-based version of the form, your withholding may not reflect the current form's income/deduction/credit fields — and TRS is explicit that it cannot give tax advice on what to enter, directing retirees to a tax professional or the IRS directly for that judgment call.

To change your election, submit a new W-4P through your MyTRSIL account's document upload, by mail, or by fax — a new form fully replaces whatever was on file before, so double-check every field rather than assuming only the line you meant to change will take effect.

TRS itself can't advise you on your withholding number

It's worth repeating TRS's own position here because retirees sometimes expect the pension system to tell them what to withhold: TRS states plainly that it cannot give tax advice, and directs members to a qualified tax professional or the IRS directly to figure out an adequate withholding amount for their situation. TRS will process whatever W-4P you submit, but the number on it is your call to make, ideally with real numbers rather than a guess.

A federal deduction may reduce taxable income for some retirees age 65 or older

For tax years 2025 through 2028, eligible taxpayers age 65 or older may claim an enhanced federal deduction of up to $6,000 per person ($12,000 for a married couple filing jointly when both qualify). It phases out when modified adjusted gross income exceeds $75,000 for single filers or $150,000 for joint filers; a valid Social Security number is required, and married taxpayers must file jointly. The deduction may be claimed whether you itemize or take the standard deduction.

This deduction lowers federal taxable income; it does not make a TRS pension tax-exempt or change Illinois's separate retirement-income subtraction. Check the current IRS instructions and your eligibility for the tax year you file.