TRS Illinois Survivor Benefit Percentage and Calculation: Tier 1 vs Tier 2

The Two Percentages That Determine Your Survivor Annuity

For an eligible surviving spouse, TRS Illinois calculates the monthly survivor annuity as a percentage of the deceased member's earned retirement benefit. That percentage depends on whether the member was classified as Tier 1 or Tier 2. Child and dependent-parent benefits use separate statutory formulas.

Tier 1 members (first contributed to TRS or a reciprocal Illinois system before January 1, 2011) generate a survivor annuity of 50% of the earned retirement benefit at death.

Tier 2 members (first contributed on or after January 1, 2011) generate a survivor annuity of 66⅔% (66.67%) of the earned retirement benefit.

That higher Tier 2 percentage is offset by Tier 2's stricter salary cap, an eight-year averaging period rather than Tier 1's four-year period, and lower annual increases — but the base survivor percentage itself is more generous than Tier 1.

How the Base Benefit Is Calculated

For a retiree death, the calculation for an eligible spouse is straightforward. TRS takes the retiree's monthly pension at the time of death and applies the tier percentage. A Tier 1 retiree drawing $4,000 per month produces a $2,000 monthly survivor annuity for the spouse. A Tier 2 retiree drawing $3,000 produces a $2,000 survivor annuity for the spouse.

For an active member death, TRS calculates the spouse's benefit using the member's earned retirement benefit, based on accumulated service credit and final average salary (FAS). Tier 1 FAS uses the highest 4 consecutive years in the last 10 years of service. Tier 2 FAS uses the highest 8 years in the last 10 (changed from consecutive to non-consecutive by Public Act 102-0016 for those retiring on or after June 1, 2021). Tier 2 also caps pensionable salary annually — $128,289.20 for 2025.

Minimum Payment Floors

The general monthly minimum is $400 for a dependent survivor, or $600 when a spouse has minor children. TRS notes that certain active-member cases can result in an amount below $400. These general minimums apply across both tiers.

Annual Cost-of-Living Adjustments

The COLA rules diverge sharply between tiers.

Tier 1 survivor annuities receive a 3% compounded annual increase, starting January 1 after the first anniversary of the benefit. Compounding means the increase applies to the current benefit, not the original amount — it grows faster over time. One exception: if the deceased retiree had elected the Accelerated Annuity Buyout (AAI), the survivor COLA drops to 1.5% simple (non-compounded), calculated on the original benefit.

Tier 2 survivor annuities receive the lesser of 3% or half the annual CPI-U change, applied as a simple (non-compounded) increase on the original survivor benefit. If the CPI change is zero or negative, there's no increase that year. This means Tier 2 survivor purchasing power erodes in real terms during periods of high inflation.

Putting It Together

A Tier 1 retiree who died with a $5,000 monthly pension leaves an eligible spouse a $2,500 survivor annuity that grows by 3% compounded each year. After 10 years, that annuity reaches roughly $3,359.

A Tier 2 retiree who died with a $3,500 monthly pension leaves an eligible spouse a $2,333 survivor annuity. Assuming 3% average CPI, the simple half-CPI increase adds about $35 per year. After 10 years, that annuity is around $2,683.

Our TRS Illinois Survivor Benefits Guide includes comparison worksheets for both tiers and walks through the full calculation for active member deaths, where the math gets more complex.

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