Last Updated: October 11, 2026 Reading Time: 8 min

If your agency is paid on the GSA payroll calendar, 2026 has 27 pay dates, and a TSP election built for 26 runs out of room on the December 18 check. For participants under 50, the December 31 check then carries a $0 contribution and, for FERS employees, no agency match for that period. The fix is one number typed into your payroll system, and it has to be in effect by pay period 26. This post gives you the number, the pay period, and the check that tells you whether you need to do anything at all.

Step One: Which Payroll Calendar Pays You

The IRS limit is applied by tax year, and an ordinary payroll contribution belongs to the year its pay date falls in, not the year the hours were worked. A pay period that ends in December but pays in January counts toward next year's limit. That is why the calendar that matters is your payroll provider's pay-date calendar, not the pay-period count on the TSP website, which has no calendar of its own.

Payroll provider Pay dates in 2026 Last 2026 pay date Does the 27-pay-date trap apply?
GSA payroll (PP1 Dec 14 to 27, 2025 through PP27 Dec 13 to 26, 2026) 27: January 2 through December 18, then December 31 December 31 (PP27) Yes. A $943 election fills the limit on the December 18 check.
IBC / FPPS (Interior and its cross-serviced agencies) 26: the 2026 earnings year runs December 14, 2025 through December 12, 2026 Pay for the period ending December 12 No. $943 is right. Switching to $908 under-contributes by about $892.
NFC (USDA, DHS components and NFC's other customer agencies) 26: official pay dates January 8 through December 24 December 24 (NFC PP24); the period ending December 26 pays January 7, 2027 No. $943 is right. Do not switch to $908.
DFAS civilian (DoD) We could not confirm the 2026 pay-date count Not confirmed Count the pay dates on your DFAS civilian pay calendar in myPay before changing anything.

IBC says it in its own words: the 2026 earnings year "has 26 pay periods from December 14, 2025, through December 12, 2026." NFC's pay period calendar shows 26 official pay dates in 2026, January 8 through December 24, with nothing on December 31. IBC counts the earnings year by pay period, not by the deposit date, so check your LES earnings-year line if your deposit arrives early. If either of those pays you, the rest of this post is a reason to leave your election alone.

GSA's 2026 payroll calendar is the one we verified with 27 pay periods and the extra pay date: December 4, 18 and 31 are all EFT pay dates, and December 31 pays pay period 27 (December 13 to 26). That is the calendar the figures below assume.

The Number to Type

The 2026 elective deferral limit is $24,500. The catch-up limit is $8,000 for participants who are 50 or older by the end of 2026, and $11,250 instead (not in addition) for participants who are 60 to 63 at the end of the year.

2026 limit Per pay date, 26 dates (IBC, NFC) Per pay date, 27 dates (GSA) Difference
$24,500 $943 $908 $35
$32,500 (age 50 and over) $1,250 $1,204 $46
$35,750 (age 60 to 63) $1,375 $1,325 $50

Dollar elections must be whole dollars, so each figure above is the exact quotient rounded up to the next dollar; the TSP stops contributions at the limit, so the last check is a little smaller (about $892 on the $908 figure). Those are the numbers for someone starting the year fresh. If you have been at $943 since January on the GSA calendar, you have already used most of the limit, and the right figure depends on which pay period your change takes effect.

Change takes effect in Periods already paid at $943 Contributed so far Room left Periods remaining New per-period amount
PP23 (Oct 18 to 31, paid Nov 6) 22 $20,746 $3,754 5 $751
PP24 (Nov 1 to 14, paid Nov 20) 23 $21,689 $2,811 4 $703
PP25 (Nov 15 to 28, paid Dec 4) 24 $22,632 $1,868 3 $623
PP26 (Nov 29 to Dec 12, paid Dec 18), the last chance 25 $23,575 $925 2 $463
PP27 only 26 $24,500 (capped) $0 1 Too late if you are under 50. PP27 contributes $0 and the 4% match is gone. At 50 or older the PP27 contribution spills into catch-up and is matched.

Computed from the $24,500 limit and the GSA pay dates; cumulative contributions are $943 times the periods paid, and each new amount is the remaining room divided by the remaining pay dates, rounded up to the next whole dollar so the limit is reached by the last pay date (the final check is a few dollars smaller). Every figure in the table stays above 5% of biweekly basic pay for a GS-13 step 5 ($197.52), so the full match survives in each remaining period. If your pay is lower, check that your new per-period amount is still at least 5% of your biweekly basic pay, because the match is computed period by period.

What a $0 Check Costs You

The agency match goes to FERS employees (CSRS employees receive no agency contributions), it is figured per pay period, and it is paid only for a period in which you contribute. 5 U.S.C. § 8432(c)(2) says the employing agency of an employee "who contributes to the Thrift Savings Fund under subsection (a) for any pay period" makes the matching contribution for that period: dollar for dollar on the first 3% of basic pay and 50 cents on the dollar for the next 2%. A $0 contribution in pay period 27 means a $0 match for pay period 27. Section 8432(c)(2) contains no year-end true-up.

The automatic 1% is different. Under 5 U.S.C. § 8432(c)(1)(A) the agency contributes 1% of basic pay for each pay period "without regard to whether the employee or Member has elected to make such contributions during such pay period." So the loss is the 4% match, not 5%.

Grade and step (2026 base, before locality) Biweekly basic pay 4% match lost in PP27 1% automatic still paid 5% of pay (the floor that keeps the full match)
GS-7 step 1 ($43,106) $1,652.00 $66.08 $16.52 $82.60
GS-11 step 1 ($63,795) $2,445.60 $97.82 $24.46 $122.28
GS-13 step 1 ($90,925) $3,485.60 $139.42 $34.86 $174.28
GS-13 step 5 ($103,049) $3,950.40 $158.02 $39.50 $197.52

Base pay from OPM's Salary Table 2026-GS; biweekly basic pay is the annual rate divided by 2,087 and rounded to cents (the hourly rate), times 80 hours (OPM's 2,087-hour divisor). Your real figures depend on your actual basic pay, so check the amount on your Leave and Earnings Statement.

The amounts look small next to a $24,500 year. They are agency money you earned by contributing and lost to a divisor.

The Real Deadline: In Effect by Pay Period 26

Two dates get mixed up every fall.

November 28, 2026 is OPM's use-or-lose annual leave scheduling date for leave year 2026. OPM's leave-year fact sheet lists it on the 2026 row. It has nothing to do with the TSP, and the 2026 leave year (January 11, 2026 to January 9, 2027) has 26 pay periods on the standard schedule. The 27-pay-period leave year was 2023.

Pay period 26 is the TSP constraint. On the GSA calendar, if your election was built on 26 pay dates, a $943 election exhausts the limit in pay period 26, so a corrected election has to be in effect for that period, paid December 18. Under 5 C.F.R. § 1600.12(d), a contribution election becomes effective no later than the first full pay period after your employing agency receives it. Received during pay period 25 (November 15 to 28), it applies to pay period 26 at the latest.

The regulation sets no agency processing cutoff, which means your payroll system does. Your system's cutoff can fall inside the pay period, so check it. IBC's year-end memo shows the practice of entering a future effective date for the change. Treat Friday, November 20, a week before the period ends, as a safe outer bound, and submit earlier than that if you can. Your own system's cutoff may be earlier still. The gentlest fix is the earliest one: an election received during pay period 22 (October 4 to 17) takes effect by pay period 23 and spreads the remaining $3,754 across five checks at $751.

Age 50 and Over: Spillover Usually Saves You

Since January 1, 2021, there is no separate catch-up election. Once your regular contributions reach $24,500, further contributions spill into the catch-up limit. Spillover contributions remain eligible for matching on employee contributions up to 5% of basic pay, producing a maximum 4% agency match plus the separate automatic 1%, because they are still employee contributions under 5 U.S.C. § 8432(a). FRTIB's final rule removed the separate election and says catch-up contributions attributable to years before 2021 are not eligible for matching. The match itself exists only for FERS employees.

So a 50-or-older participant sitting at $943 on the GSA calendar does not lose the pay period 27 match. The December 31 contribution spills into catch-up and is matched. The trap comes back only if you are also maxing the combined limit ($32,500, or $35,750 at 60 to 63) with a 26-period figure: then the combined limit is exhausted before pay period 27 and the last check is $0 again. If you are in a high-earner bracket subject to mandatory Roth catch-up, see the SECURE 2.0 Roth catch-up post.

How to Change the Election

  1. Open your agency's payroll self-service system (Employee Express, myPay, EPP or FPPS) or complete Form TSP-1 for your HR office.
  2. Find the TSP contribution election and choose a dollar amount per pay period rather than a percentage. A dollar election gives you exact control; either type stops automatically when the IRS limit is reached.
  3. Enter a whole-dollar election calculated from your actual year-to-date contributions and remaining pay dates, and set a future effective date if your system offers one.
  4. Check your Leave and Earnings Statement for the first pay date after the change to confirm the new amount posted.
  5. After the December 18 pay date, confirm your year-to-date contributions leave room for the December 31 check.

Check Your Own Numbers

Use the free TSP Contribution Calculator to enter your current per-pay-period election, the pay periods already elapsed before your change takes effect, and 27 in the editable total-pay-periods field. It assumes one flat election for the elapsed periods and returns an even-spread amount for the remaining periods, rounded down to a whole dollar, plus the agency match you leave on the table for the year. Because it rounds down, add $1 only when the remaining-room quotient has a fractional dollar, and check that the final capped contribution is still at least 5% of your biweekly basic pay so the last match is kept. Try it now →

Frequently Asked Questions

Do I need to change my TSP election because 2026 has 27 pay periods?

Only if your payroll provider's 2026 calendar has 27 pay dates. GSA's does, with December 31 as the 27th. IBC's 2026 earnings year has 26 pay periods, and NFC's calendar shows 26 official pay dates, January 8 through December 24. Count the pay dates on your agency's calendar before changing anything.

What exact dollar amount per pay period maxes the TSP across 27 pay dates in 2026?

$908 for the $24,500 limit; $1,204 for the $32,500 limit at age 50 and over; $1,325 for the $35,750 limit at ages 60 to 63 at year-end. Across 26 pay dates the figures are $943, $1,250 and $1,375.

I have contributed $943 every pay period this year on the GSA calendar. What do I change it to?

It depends on the pay period in which the change takes effect. Effective pay period 23: $751. Pay period 24: $703. Pay period 25: $623. Pay period 26: $463. A change effective only in pay period 27 is too late, because the limit is already reached; participants 50 or older can keep contributing under the catch-up limit.

What is the real deadline to change the election?

On the GSA calendar, if your election was built on 26 pay dates, it must be in effect for pay period 26 (November 29 to December 12, paid December 18). Under 5 C.F.R. § 1600.12(d) an election is effective no later than the first full pay period after your agency receives it, so it must be received during pay period 25 (November 15 to 28) at the latest, and your agency's processing cutoff may fall earlier than the last day. Submit it now.

How much agency money do I lose if my contribution is $0 on the December 31 check?

For FERS employees, the 4% match for that period: about $66 at GS-7 step 1, $98 at GS-11 step 1 and $139 at GS-13 step 1 on base pay before locality. The 1% automatic contribution is paid regardless under 5 U.S.C. § 8432(c)(1)(A).

I am 50 or older. Does spillover protect my match?

Yes, if you are covered by FERS and only maxing the $24,500. Since 2021 there is no separate catch-up election; contributions above the limit spill into catch-up and, as employee contributions, remain eligible for matching on employee contributions up to 5% of basic pay, producing a maximum 4% agency match plus the separate automatic 1%. It does not help if you are also maxing the combined $32,500 or $35,750 limit with a 26-period figure.

My agency is paid by NFC or DFAS. Do I have 27 pay dates?

NFC: no. NFC's 2026 official pay dates run January 8 through December 24, 26 of them, and the period ending December 26 is paid January 7, 2027. Keep the 26-period figure. DFAS: we could not confirm the DFAS civilian pay-date count for 2026, so count the pay dates on your DFAS civilian pay calendar in myPay before changing anything.

Is November 28 the TSP deadline?

No. November 28, 2026 is OPM's use-or-lose annual leave scheduling date. On the GSA calendar, if your election was built on 26 pay dates, the TSP constraint is that the corrected election is in effect for pay period 26, which means your agency receives it during pay period 25 at the latest.

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