Illinois State Employee Pay Dates & Paycheck Guide

The pay calendar

Most State of Illinois agencies pay semi-monthly: two pay periods a month, running the 1st to the 15th and the 16th to the last day, with pay released about three to five business days after each period closes. That is 24 pay dates a year. The Comptroller publishes a pay schedule book for each calendar year listing every period beginning date, ending date and release date across the numbered schedules, and it is the authoritative source for exact dates.

A few employers within state government run differently. Some are on a monthly schedule with twelve periods, and the Illinois Tollway runs a biweekly calendar with 26. If you are checking a specific date, confirm which schedule your agency uses rather than assuming the semi-monthly default.

Semi-monthly is not the same as biweekly

The distinction confuses new state employees constantly, so it is worth setting out plainly:

Federal withholding adjusts for the frequency automatically — Publication 15-T annualizes whatever period you are on, so 24 larger checks and 26 smaller ones produce the same annual withholding on the same salary. The calculator above is set to semi-monthly; switch the frequency to see the comparison directly.

What comes off a State of Illinois paycheck

The federal, Illinois and FICA lines work exactly as they do anywhere else in the state, and they are broken down on the deductions guide. Three further lines are particular to state employment.

The SERS contribution

Every SERS member contributes a fixed percentage of salary, and the rate depends on two things: which benefit formula covers your position, and whether that position is coordinated with Social Security.

These rates are the same for Tier 1 and Tier 2 members, which is one of the more striking features of the Illinois pension structure — Tier 2 members contribute identically to Tier 1 members for a materially smaller benefit. The alternative formula covers State Police, correctional officers, conservation police, investigators and similar security roles, and its higher contribution buys a substantially richer pension. Whether you are coordinated determines whether you also pay FICA on the same wages. The benefit those contributions buy is worked out on the SERS pension calculator.

Deferred compensation

The state offers a 457(b) Deferred Compensation Plan on top of the pension, and new hires who contribute to SERS are automatically enrolled at 3% pre-tax from the pay period after 30 days of employment, with an opt-out available. The 2026 limits are $24,500, $32,500 from age 50, and $35,750 in the enhanced catch-up window for ages 60 to 63, with a separate special catch-up of up to $49,000 available in the three years before normal retirement age.

Pre-tax contributions reduce federal and Illinois income tax immediately but never reduce Social Security or Medicare — a distinction that surprises people the first time they compare a contribution increase against the change in net pay. Roth contributions are also available and reduce nothing now. Because Illinois exempts qualified retirement distributions in full regardless, the Illinois side of the traditional-versus-Roth question is essentially settled in favor of pre-tax; the federal comparison is what decides it.

Union dues

Roughly 93% of state employees are union represented, most under the AFSCME Master Contract running from 1 July 2023 to 30 June 2027. Since the Supreme Court's decision in Janus there is no fair share deduction: dues are withheld only where the individual employee has requested it, and the contract reflects that.

Pay plans and step increases

Bargaining unit positions sit on classification pay tables with step progression through the contract's schedules, and the Master Contract's Schedule A contains rate tables effective on several dates across the four-year term. Merit Compensation employees — the non-union side — sit on MS-numbered salary ranges with a minimum and a maximum and no automatic steps; movement comes through promotion or in-range adjustment, generally capped at 5% of base salary per action under the Central Management Services pay procedures. Broad-band ranges exist for some roles.

If you are comparing an offer against what people in the role actually earn, the Comptroller's public salary database shows year-to-date gross pay by name, title and agency. Read it carefully: gross pay includes overtime and reflects however much of the year the person worked, so it is frequently not the position's salary. The state employee salary page goes into how to use it without drawing the wrong conclusion.

What the money is worth after tax

A $70,000 state salary paid semi-monthly comes to $2,916.67 gross per check. For a single filer with no dependents and no pre-tax deductions, federal withholding takes $273.75, Illinois takes $144.38, and FICA takes $223.12 — leaving about $2,275.42 before the SERS contribution, deferred comp and insurance premiums come off. Add a 4% SERS contribution and that is a further $116.67 per check.

The calculator above is the general Illinois engine set to semi-monthly, so enter your pre-tax insurance premiums and deferred compensation in the deduction fields and it will handle them correctly. For the SERS contribution itself, treat it as a pre-tax retirement deduction — it reduces income tax but not FICA, exactly like a 401(k).