Illinois Pension Calculator

State Employees' Retirement System of Illinois: How the pension works

Benefit formula

The formula above reflects the base structure. Actual benefits depend on your membership tier, bargaining unit, hire date, and whether any additional credits apply. Members hired after benefit restructuring (which happened in most states between 2008 and 2014) are often in less generous tiers than longer-tenured employees.

If you're unsure which tier you're in, your annual benefit statement from SERS will show your projected benefit and current accrued amount. Compare those figures to the formula to back into your effective multiplier.

Covered employees

State Employees' Retirement System of Illinois covers state government employees, except those in positions covered by another state system (teachers outside Chicago use TRS; university employees use SURS; judges use JRS). If you're an Illinois public employee and aren't sure whether you're in SERS or a separate retirement system (teachers, police, fire, and judges sometimes have different plans), check your pay stub: if a pension contribution is being deducted and forwarded to SERS, you're in this system.

Vesting and early separation

You need 10 years of service credit (8 for Tier 1 members, first hired before January 1, 2011) to vest. Before vesting, leaving public employment generally gets you back only your own employee contributions, if your plan required any. Once vested, you're entitled to a future pension benefit even if you leave before reaching retirement age, though you may need to wait until a specific age to start receiving payments.

Leaving before vesting and taking the contribution refund is usually a mistake unless you have a specific cash need. That money grew tax-deferred, and forfeiting the pension benefit means you gave up the employer-funded portion entirely. If you're close to the vesting date, staying is almost always worth it.

Lump sum option

SERS pays a monthly annuity, but two voluntary buyouts run through 2028 while bond funds last. Tier 1 members retiring by June 1, 2028 can take the COLA buyout: a lump sum equal to 70% of the difference in present value between the 3% compounded COLA and a reduced, delayed COLA. Inactive vested members (Tier 1 with 8 years or Tier 2 with 10) can take the Total buyout through May 31, 2028: a lump sum equal to 60% of the present value of their earned benefit in place of the pension. Members who leave state employment can also refund their contributions, without interest. Tier 1 covers members first hired before January 1, 2011. TRS and SURS run their own versions of both buyouts.

Any lump sum you take is paid for out of the lifetime benefit, through a lower monthly amount or pension months you don't collect. Use the calculator below to put a present value on the full monthly benefit and compare it with the cash. If the cash is well below that value, the annuity is the better deal.

What the present value calculation tells you

The present value does three jobs. It lets you compare the pension with alternatives, such as leaving for a private-sector job with a 401(k). It shows what you give up in exchange for SERS's lump sum. And it puts a number on the retirement income you've built, which feeds Social Security timing and IRA drawdown decisions.

The IRS 417(e) formula uses three segment rates to discount future pension payments back to today. At current rates (4.07%, 5.15%, 6.01% for 2026), a $2,500/month pension starting at 65 is worth about $369,000 as a single sum under the IRS 2026 mortality table. Public plans don't have to offer that amount, and most don't offer a lump sum at all.

Coordinating your SERS pension with Social Security

Social Security coverage depends on the position. Some state and local government jobs are outside Social Security, and those jobs don't earn Social Security benefits. Check your pay stub: if no Social Security (OASDI) tax is withheld, that job probably isn't covered. Medicare tax on its own doesn't mean the job is covered.

If you have private-sector work history where you did pay into Social Security, the Windfall Elimination Provision (WEP) and Government Pension Offset (GPO) previously reduced Social Security benefits for workers with government pensions. Both were repealed by the Social Security Fairness Act of 2023, signed January 5, 2025, effective for benefits payable after December 2023. SSA finished paying the retroactive amounts in 2025. If you think yours is missing, contact SSA.

If your public employment included Social Security contributions, which varies by state and by position, then Social Security timing still matters, and the break-even analysis is worth running separately. The Social Security break-even calculator on this site handles that calculation.