Abaque 06 · Capacity

The shelter ceiling

Two statutory shapes govern how much can go into a workplace plan. The match ramp rises steeply and then stops dead at a kink written into the Code — past it, the employer contributes nothing further. The deferral ceiling steps up at 50 and again at 60, and then, uniquely among retirement provisions, steps back down at 64. One is the only unconditional rule in this whole series; the other is a window that shuts.

Match saturates—
Your ceiling—
Rate to fill it—
RegisterSheet 00
Sheet06 · Rev A
Inputs

Enter the chart here

Safe harbor design
—
Salary$120,000
—
Age57
—
Your deferral rate3%
—
Fig. 1

The match ramp, and where it stops

Basic — 100% of 3%, then 50% of 2% Enhanced — 100% of 4% QACA — 100% of 1%, then 50% of 5% Free money still on the table
All three are written into the Code, so the shape of the ramp is statutory even though your employer picks which one to adopt. Each has a kink and then a flat. Left of the kink the employer is paying you to save; right of it they are not, and every further point of deferral is worth exactly what any other tax-deferred dollar is worth — no more. Notice QACA saturates lowest and latest: 3.5% of pay, and not until you defer 6%.
Match captured——
Free money forgone——
Return on your next dollar——
Total into the plan——
Fig. 2

The ceiling by age — and the year it drops

Employee deferral ceiling Ceiling falls here Super catch-up window, ages 60–63
Almost every age threshold in retirement law opens something. This one shuts. The super catch-up is available at 60, 61, 62 and 63 and then reverts at 64 — a four-year window worth — in extra shelter, after which the ceiling is lower than it was the year before. It is the only place in the Code where waiting costs you capacity outright.
Fig. 3

What rate it takes to fill the shelter

Fill 402(g) Fill 402(g) + age-50 catch-up Fill the age 60–63 ceiling
The ceilings are fixed dollar amounts, so the rate needed to reach them is a hyperbola in salary — this is the iso-salary fan. It carries the uncomfortable corollary: the lower the salary, the higher the rate required, and below a certain income the statutory ceiling is simply unreachable on any plausible savings rate. The limits are generous only to people who were already going to be fine.
Calculation

Every step, at your inputs

Table 1

The ladder, age by age

Age402(g)Catch-upEmployee ceiling Rate to fillChangeNote
Method, and the two rules people get wrong

The match is a tiered integral, not a percentage

A design like “100% of the first 3%, then 50% of the next 2%” is a piecewise function of your deferral rate, integrated band by band:

match(r) = Σ over tiers (min(r, tier.upTo) − previous.upTo) × tier.rate

which is why the answer to “what is my match worth?” depends entirely on where you are standing. The first three points of pay earn a 100% instant return. The fourth and fifth earn 50%. The sixth earns nothing at all. No investment decision in this series comes close to the first band, and no amount of fund selection compensates for missing it.

Rule one: the match is capped by compensation, not by the match

Pay above the 401(a)(17) compensation limit is invisible to the plan. Beyond it the match stops growing even though the salary keeps going, so the match expressed as a percentage of actual pay quietly falls.

Rule two: catch-up sits outside 415(c), and from 2026 it may be forced to Roth

The 415(c) annual additions limit covers employee deferrals plus employer contributions plus after-tax money — but not catch-up. A participant aged 50 or over can therefore reach 415(c) plus the catch-up on top.

Separately, and new for 2026: if your prior-year FICA wages from that employer exceeded the SECURE 2.0 threshold, your catch-up contributions must be Roth. This is not a choice, and it lands exactly when catch-up capacity is largest. It does not reduce how much you may shelter; it removes the deduction, which changes the answer sheet 02 gives about which bucket to use.

What is not modelled

  • Your actual plan. Whether it offers after-tax contributions, in-plan Roth conversion, true-up on the match, or a non-safe-harbor formula entirely. Plan documents beat statute for anything the statute leaves open.
  • Vesting. Safe harbor match is immediately vested; other employer money need not be.
  • Timing within the year. A plan without true-up can shortchange someone who front-loads deferrals and hits 402(g) early, because the per-payroll match stops when deferrals stop. This is a real and common trap that no statutory chart can show.
  • Whether pre-tax or Roth is better. That is sheet 02, and it turns only on the two tax rates.

Confidence

All three safe harbor formulas and every contribution limit on this sheet are Verified against IRS Notice 2025-67 and the Code. The 401(a)(17) compensation limit is Approx for 2026. Flags travel with the values from the register on sheet 00.

This is arithmetic, not advice. The match ramp is the closest thing in this series to an unconditional rule — capturing the full match is nearly always worth doing — but “nearly always” is not “always,” and someone without an emergency fund or carrying high-rate debt may rationally do otherwise. Dollar figures are approximate and re-indexed. Check your own plan document; it governs everything the statute leaves open.
Indexed figures are re-set every January and this snapshot will go stale. Get notified when they are re-verified → · All twelve sheets