Illinois TRS COLA: Tier 1's Automatic 3% vs. Tier 2's Delayed, Smaller Increase

Tier 1: an automatic, compounding 3%

Tier 1 retirees receive an automatic annual increase of 3% of their current annuity, applied each January 1 on or after the first anniversary of retirement, generally once the retiree has reached at least age 61. Because this increase is calculated on the current (already-increased) annuity rather than the original amount, it compounds over time — each year's 3% is 3% of a slightly larger number than the year before, which meaningfully increases the total benefit paid out over a long retirement compared to a flat, non-compounding adjustment of the same headline percentage.

Tier 2: smaller, not compounded, and delayed until age 67

Tier 2 retirees receive an annual increase equal to the lesser of 3% or half of the Consumer Price Index increase measured as of the preceding September. The adjustment is not compounded: each year's increase is calculated from the originally granted annuity, not the amount after earlier increases. The first increase is effective on the January 1 occurring on or after the later of the member's age-67 date or first annuity anniversary. Tier 1's first increase instead follows the later of age 61 or the first anniversary. These timing and calculation rules come directly from the TRS Tier 2 and Tier 1 member guides.

This combination — a smaller possible percentage, no compounding, and a later start — means Tier 2's COLA mechanism produces meaningfully less total benefit growth over a comparable retirement length than Tier 1's, even setting aside every other difference between the two tiers' benefit formulas.

Why this gap exists

The Tier 2 structure, including its COLA mechanism, was created by Illinois legislation applying to members who first contributed to TRS on or after January 1, 2011, largely as part of a broader effort to reduce the state's long-term pension funding obligations. The COLA difference is one of several Tier 2 provisions (alongside the higher vesting requirement and later retirement age) designed to reduce the system's total long-run benefit payout for newer members relative to Tier 1's terms.

What this means for retirement planning

If you're a Tier 2 member, it's worth explicitly building the slower, delayed COLA mechanism into your retirement income planning rather than assuming your pension will keep pace with inflation the way an older colleague's Tier 1 pension might. Because the difference compounds (or, in Tier 2's case, doesn't) over what could be a multi-decade retirement, even a seemingly modest annual percentage difference becomes a substantial gap in total benefits received over time — a gap worth planning around with additional personal savings if you're relying primarily on your TRS pension for retirement income.

A simplified side-by-side comparison over time

To make the practical difference concrete: a Tier 1 retiree starting with a $40,000 annual annuity and receiving 10 full 3% increases would reach about $53,756 before other changes. A Tier 2 retiree with the same annuity and 10 full increases at the maximum 3% would reach $52,000, because each increase is a fixed $1,200 against the original annuity. The Tier 2 increases also begin later: the first is on the later of the age-67 or first-anniversary January 1. Actual Tier 2 increases may be lower than 3% when half the CPI increase is lower.

This simplified comparison assumes 10 full years of increases for each tier and the maximum possible 3% Tier 2 adjustment; it does not account for the later Tier 2 start in a shared retirement timeline. Actual Tier 2 increases may be lower when half the CPI increase is below 3%. Treat the figures as an illustration of the calculation, not a forecast of future CPI or lifetime payments.

Where to check your own COLA start date and rate

TRS's Tier 1 and Tier 2 member guides state the age and anniversary triggers described above. Your precise effective date still depends on your annuity start date and recorded age, so check your own TRS account or ask TRS if a retirement decision turns on the first increase date.

It's also worth asking TRS directly whether any pending state legislation could affect your specific COLA calculation, since Illinois has periodically considered pension-related legislative changes — your annual statement or a direct inquiry is a more current source than a general guide like this one for anything time-sensitive.