One more year of service is worth $83.33 a month on a $60,000 AFC (our arithmetic on the formula).
The facts
- If you're vested, you may be able to buy service for teaching out of state or in a private school, leaves of absence, military service and more, up to 5 years in total. Most types need a full year of Montana TRS service after the period you're buying.MCA 19-20-405; Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), pp. 4, 7
- If you joined on or after July 1, 1989, most purchases cost the full actuarial cost. The price rises as your pay grows, so ask Montana TRS for a quote early.Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), pp. 5, 11; Montana TRS web page: Understand Your Benefits
- You can buy back service you withdrew by repaying the refund plus interest. Purchases must be finished before Montana TRS processes your retirement application.MCA 19-20-427; Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), pp. 4, 8
Service purchases (out-of-state, private school, leave, non-USERRA military/Red Cross/merchant marine, extension service, MUS-RP) are limited to 5 years in total. Most require being vested with one full year of membership service after the period purchased. Members who joined on or after July 1, 1989 pay the full actuarial cost; earlier members pay years x combined rates x first-year salary plus interest. Purchases must be finished before Montana TRS processes the retirement application, and can't be made after benefits start. Payments: lump sum, rollover, or 3 to 60 monthly payments (pre-tax employer pick-up possible). Redeposits of withdrawn service and corrections of reporting errors are not subject to the 5-year limit. MCA 19-20-405, 19-20-401(11), 19-20-414, 19-20-415; Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), pp. 4-7; Montana TRS web page: Understand Your Benefits (Purchasing Service)
What you can buy
| Type | Limit |
|---|---|
| Withdrawn service (redeposit)Re-purchase withdrawn service: refund plus interest at the actuarially assumed rate.MCA 19-20-427; Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), pp. 7-8 | no limit |
| Out-of-state or private teachingPublic or private teaching outside Montana TRS in the U.S. or abroad.MCA 19-20-402, 19-20-408; Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), pp. 10-11 | 5 years |
| Military, Red Cross, merchant marineActive service in the U.S. armed forces, Red Cross or merchant marine (non-USERRA).MCA 19-20-404; Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), p. 13 | 2 years |
| USERRA military leaveUSERRA military leave: free vesting credit; buy up to 5 years for the benefit by paying member contributions (no interest if bought within 5 years of return).Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), pp. 12-13 | 5 years |
| Korea or Vietnam serviceFree credit for up to 4 years of uniformed service in the Korean or Vietnam conflicts (vested members).Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), p. 12 | 4 years |
| Work-injury leaveLeave for an employment-related injury with workers' compensation.MCA 19-20-411; Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), p. 13 | 2 years |
| PERS service transferTransfer PERS defined-benefit service and contributions (after leaving PERS employment).MCA 19-20-409; Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), p. 9 | no limit |
Purchases together can't top 5 years. Payment: a lump sum, a rollover, or 3 to 60 monthly payments. MCA 19-20-405, 19-20-401(11), 19-20-414, 19-20-415; Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), pp. 4-7; Montana TRS web page: Understand Your Benefits (Purchasing Service)
Extra duty paid by stipend
Stipend-paid extra duty for someone not otherwise employed: entry-level teacher base pay / 187 = daily rate; stipend / daily rate = days; days / 180 = portion of a year. MCA 19-20-401(8)(d)(iii); Calculating and Reporting Extra Duty Service Credit fact sheet (May 15, 2025), pp. 2-3
The district's entry-level teacher base pay is $38,000. $38,000 ÷ 187 = a daily rate of $203.21.
Calculating and Reporting Extra Duty Service Credit fact sheet (May 15, 2025), pp. 2-3| Stipend | Days | Hours | Share of a year |
|---|---|---|---|
| $6,000 | 29.53 | 206.71 | 16.4% |
| $4,800 | 23.62 | 165.34 | 13.1% |
Days and hours are Montana TRS's figures, which our engine matches. The share of a year is our arithmetic: days ÷ 180.
How service is counted
Creditable service is awarded by fiscal year (July 1-June 30); no more than 1 year per fiscal year. MCA 19-20-401(6), (9); Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), pp. 2-3
A day of 7+ hours is a full-time day. Full-time service is at least 180 days in a fiscal year, at least 140 hours a month in 9 months, or full-time under an approved alternative calendar of at least 1,080 hours. Part-time service is credited pro rata. MCA 19-20-401(7); Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), pp. 2-3
You can't buy service to become vested. MCA 19-20-101(35); Montana TRS web page: Understand Your Benefits (Becoming Vested; Purchasing Service); Creditable Service and Service Purchases fact sheet (Aug. 5, 2026), p. 1 See what extra years add in the calculator or on one more year.
Questions
What service can I buy in Montana TRS?
Out-of-state and private school teaching, some leaves, non-USERRA military service and more, up to 5 years in total; plus redeposits of service you withdrew, which don't count toward the 5.
What does it cost?
If you joined on or after July 1, 1989, most purchases cost the full actuarial cost. Ask Montana TRS for a quote.
How does extra-duty pay count?
If you're paid only a stipend, it's turned into days: the entry-level teacher base pay ÷ 187 gives a daily rate; the stipend ÷ that rate gives days; 180 days is a year.
Source: Montana TRS: Understand Your Benefits (web page) and fact sheets, Fetched Nov. 12, 2026; fact sheets revised 2019-2026, fact sheets: Calculating and Reporting Extra Duty Service Credit pp. 2-3; Creditable Service and Service Purchases pp. 1, 2-3, 4-7, 7-8, 9, 10-11, 12-13. Also: MCA §§ 19-20-101, 19-20-401, 19-20-402, 19-20-404, 19-20-405, 19-20-408, 19-20-409, 19-20-411, 19-20-414, 19-20-415, 19-20-427. Last reviewed .