Tier One
Before July 1, 2013
Tier One: became a member before July 1, 2013 (and never withdrew).
MCA 19-20-101(33)-(34), 19-20-603(3)(d), (4); Montana TRS web page: Understand Your Benefits (Tier 1 and Tier 2 Membership); Withdrawing TRS Membership fact sheet (Apr. 10, 2026), p. 1Tier Two
On or after July 1, 2013
Tier Two: became a member on or after July 1, 2013 (or a former member who withdrew and came back after July 1, 2013).
MCA 19-20-101(33)-(34), 19-20-603(3)(d), (4); Montana TRS web page: Understand Your Benefits (Tier 1 and Tier 2 Membership); Withdrawing TRS Membership fact sheet (Apr. 10, 2026), p. 1If you were Tier One, withdrew your account and later became a member again, you're Tier Two, even if you buy the withdrawn service back. The calculator has a box for this under More details.
MCA 19-20-101(33)-(34), 19-20-603(3)(d), (4); Montana TRS web page: Understand Your Benefits (Tier 1 and Tier 2 Membership); Withdrawing TRS Membership fact sheet (Apr. 10, 2026), p. 1A former member who withdrew and returns is Tier Two if they 'became a member again after July 1, 2013' (statute, valuation) or 'on July 1, 2013, or later' (Montana TRS glossary). The difference matters only for someone who rejoined exactly on July 1, 2013; the fact sheets and MCA 19-20-603(4) say any Tier One member who withdraws returns as Tier Two.
MCA 19-20-101(34), 19-20-603(4); Montana TRS web page: Glossary of Terms (tier two member); Actuarial Valuation (July 1, 2025), p. 47
What your tier changes
| Tier One | Tier Two | |
|---|---|---|
| Who | Joined before July 1, 2013 and never withdrew | Joined on or after July 1, 2013, or withdrew and came back |
| Full benefit | Age 60 with at least 5 full years of creditable service; or Any age, credited with full-time or part-time creditable service in 25 or more years | Age 60 with at least 5 full years of creditable service; or Age 55, credited with full-time or part-time creditable service in 30 or more years |
| Early (reduced) | From 50 with 5 years | From 55 with 5 years |
| Formula | 1/60 (1.6667%) × AFC × years | 1/60 × AFC × years; 1.85% at 60 with 30 years |
| AFC | Highest 3 consecutive fiscal years | Highest 5 consecutive fiscal years |
| You pay | 7.15% + 1% supplemental = 8.15% | 8.15% |
| GABA | 1.5% a year | 0.5% to 1.5% (now 0.5%) |
MCA 19-20-101(33), 19-20-801(1), 19-20-802(1)(a), 19-20-804(1), 19-20-805(1)(a); Montana TRS web page: Understand Your Benefits (Tier 1 Service Retirement; Standard Benefit Calculation Formula); Actuarial Valuation (July 1, 2025), pp. 47-48, Appendix B; MCA 19-20-101(34), 19-20-801(2)-(3), 19-20-802(1)(b), 19-20-804, 19-20-805(1)(b); Montana TRS web page: Understand Your Benefits (Tier 2 Service Retirement; Tier 2 Professional Option); Actuarial Valuation (July 1, 2025), pp. 47-48, Appendix B; Montana TRS FY2025 ACFR, p. 19 (Summary of Benefits); MCA 19-20-602, 19-20-608; Montana TRS web pages: Contribution Rates and Understand Your Benefits (Interest rate credited to member accounts); Actuarial Valuation (July 1, 2025), pp. 49-51, Appendix B (Contributions; Interest on Member Contributions)
The facts
- Montana TRS covers teachers, administrators and other people whose jobs are mainly educational in Montana public schools, community colleges and some state agencies. You join from your first day.Montana TRS New Member handout (Feb. 25, 2025), p. 1; Montana TRS FY2025 ACFR, p. 18
- Your tier depends on when you joined: Tier One if you became a member before July 1, 2013 and never withdrew; Tier Two if you joined on or after July 1, 2013.MCA 19-20-101(33)-(34); Montana TRS web page: Understand Your Benefits
- If you were Tier One, withdrew your account and later came back, you return as Tier Two, even if you buy back the withdrawn service.MCA 19-20-603(4); Withdrawing TRS Membership fact sheet (Apr. 10, 2026), p. 1
- School office, kitchen and custodial staff and bus drivers are usually in Montana PERS, not Montana TRS. University System employees hired since 1993 are in the MUS Retirement Program instead.Working After Retirement fact sheet (Mar. 26, 2026), p. 4; 2023 Legislative Summary, p. 3
- You're vested after 5 full years of creditable service. Vested members can get a monthly benefit for life. You can't buy service to become vested.MCA 19-20-101(35); Montana TRS web page: Understand Your Benefits
- Tier One: you can retire with full benefits at 60 with 5 years of service, or at any age with 25 years.MCA 19-20-801(1); Montana TRS web page: Understand Your Benefits; Actuarial Valuation (July 1, 2025), p. 48
- Check with Montana TRSThe Tier One 25-year rule counts years in which you were credited with full-time or part-time service. Montana TRS's web page describes it as service reported in 25 fiscal years. Check with Montana TRS how your part-time years count.The statute's wording ('creditable service in 25 or more years') and the web page can be read two ways.MCA 19-20-801(1)(b); Montana TRS web page: Understand Your Benefits
- Tier Two: you can retire with full benefits at 60 with 5 years of service, or at 55 with 30 years.MCA 19-20-801(2); Montana TRS web page: Understand Your Benefits
- You must stop all Montana TRS-reportable work with every employer and apply. Benefits start no earlier than the first of the month after your last day. For example, a last day of June 10 gives a July 1 retirement date.MCA 19-20-703(2), 19-20-801(4); Terminating Employment and Retiring fact sheet (July 1, 2023), p. 2
- Montana TRS asks for your completed application packet at least 60 days before your planned retirement date. Request it about six months ahead.Montana TRS web page: Retirement Prep
The web page lists Tier One retirement at 'any age with 25+ years of creditable service' and also 'any age as long as service was reported within 25 fiscal years'. The statute says 'credited with full-time or part-time creditable service in 25 or more years'; the valuation and ACFR say '25 years of service'. We model a count of fiscal years with any credited service and flag it.
Montana TRS web page: Understand Your Benefits (Tier 1 Service Retirement); MCA 19-20-801(1)(b); Actuarial Valuation (July 1, 2025), p. 48; Montana TRS FY2025 ACFR, p. 19
The statute and web page can be read as counting fiscal years with any credited service (part-time included), rather than 25 (30) full years of service.
Optional input yearsWithService (fiscal years with any credited service); defaults to serviceYears
What would settle it: Montana TRS's written interpretation of MCA 19-20-801(1)(b) and (2)(b), or an ARM 2.44 rule.
See how each tier's rules play out in the calculator, or read about early retirement and the formula.
Questions
What decides my Montana TRS tier?
The date you became a member. Before July 1, 2013: Tier One. On or after: Tier Two.
I was Tier One, took a refund and came back. Which tier am I?
Tier Two. A Tier One member who withdraws and returns comes back as Tier Two, even after buying the withdrawn service back.
Does my tier change the formula?
Both tiers use 1/60 (1.6667%) a year. Tier One averages your highest 3 years and Tier Two your highest 5. Only Tier Two has the 1.85% option.
Source: Montana TRS: Understand Your Benefits (web page) and fact sheets, Fetched Nov. 12, 2026; fact sheets revised 2019-2026, fact sheets: Creditable Service and Service Purchases p. 1; Terminating Employment and Retiring p. 2; Withdrawing TRS Membership p. 1; Working After Retirement p. 4. Also: Montana TRS web pages: Contribution Rates, What is GABA, Retirement Prep; Actuarial Valuation (July 1, 2025); FY2025 Annual Comprehensive Financial Report; New Member handout (Feb. 25, 2025); 2023 Legislative Summary; MCA §§ 19-20-101, 19-20-401, 19-20-602, 19-20-603, 19-20-608, 19-20-703, 19-20-719, 19-20-801, 19-20-802, 19-20-804, 19-20-805. Last reviewed .