Buying service is one way to reach full-pension age sooner or raise your percentage; the other is working one more year. The years count in the pension formula and toward the early-retirement rules. Add years to TRS Illinois's Tier 2 example in the calculator to see the difference.
What you can buy, and the cost
Optional service: out-of-system public teaching (max 2/5 of TRS Illinois service, overall max 10 years, after 5 years of TRS Illinois/CTPF/SURS service), part-time teaching (July 1969-June 1990), substitute/homebound, leaves of absence and involuntary layoffs, pregnancy/adoption before July 1983 (max 3 years combined), paid student teaching (on or after Aug. 7, 2019), military (up to 5 years, only 2 not immediately following teaching), private school (max 2 years, at least 10 years of contributing TRS Illinois service, apply by June 30, 2028), and repayment of refunds. Most cost the contributions that would have been due plus interest usually at 6%; military-not-following-teaching and private school cost the total normal cost. THIS Fund contributions are also due for service on or after July 1, 1995. Most purchases must be completed before retirement. Tier 1 Guide pp. 10-13, Ch. 6 Optional Service Credit
How to pay
Lump sum or installments (min $50) to TRS Illinois; tax-sheltered rollovers accepted. The 2.2 upgrade cannot be paid in after-tax installments. Tier 1 Guide p. 14, Ch. 7 Payment Options
Credit you get without buying
Unused sick leave adds up to 2 years (340 days) at retirement, at no cost. 205 days is 1.206 years. Tier 1 Guide pp. 8-9, Sick leave and Example
What the guides say
- You can buy credit for out-of-system public teaching, leaves of absence, layoffs, military service, up to 2 years of Illinois private school (apply by June 30, 2028), paid student teaching, and refunded TRS Illinois service.Tier 1 Guide pp. 10-13; TRS Illinois Tier 2 slides, slide 12
- Most purchases cost the contributions you would have paid plus interest, usually 6%, and must be finished before you retire.Tier 1 Guide p. 10, Cost
- Out-of-system service is limited to two-fifths of your TRS Illinois service and 10 years total, and needs 5 years of TRS Illinois, CTPF or SURS service after it.Tier 1 Guide pp. 10-11
- You can pay in a lump sum, in installments of at least $50, or by rolling over pre-tax money from a 403(b), 457(b), IRA or similar plan.Tier 1 Guide p. 14, Ch. 7 Payment Options
Questions
What service can I buy from TRS Illinois?
Out-of-system public teaching, leaves of absence, involuntary layoffs, military service, some part-time, substitute and private-school teaching, paid student teaching, and refunds you took earlier.
What does it cost?
Usually the contributions you would have paid, plus interest (usually 6%). Some types cost the full normal cost.
When do I have to finish paying?
Most purchases must be finished before you retire.
Source: TRS Tier 1 and Tier 2 Member Guides, September 2026, Tier 1 Guide pp. 8, 9, 10, 11, 12, 13, 14; Tier 2 Guide pp. 10, 11, 12, 13, 14, 15, 18; Tier 2 meeting slides 12, 14. Last reviewed .