Should you choose the monthly sum crediting method?
Only if you believe the market is more likely to grind slowly higher than to swing hard in either direction. Monthly sum rewards a year of small, steady monthly gains better than almost any other crediting method, because none of those months get wasted below a single annual cap. The same design punishes one sharp down month by counting it in full while your good months stayed capped, so a single rough stretch can erase a year of gains. If you want the smoother, more predictable outcome most retirees prefer, an annual point-to-point or a participation rate strategy is usually the better starting point.
What monthly sum crediting is
A fixed index annuity ties your interest credit to the movement of a market index, and monthly sum is one of a handful of formulas carriers use to translate that movement into a number on your statement. Instead of looking at the index once a year, the way an annual point-to-point contract does, monthly sum checks it on each of your twelve monthly contract anniversaries.
Every month that shows a gain gets trimmed down to a set ceiling before it counts. Every month that shows a loss counts exactly as it happened, with no floor at the monthly level. Add the twelve results together at your contract anniversary, and whatever that sum comes to, positive or otherwise, becomes your credit for the year. A total at or below zero simply means you earned nothing that year; it never means your account value drops.
That structure creates a lopsided bet. Small, steady gains month after month rack up quickly because none of them are wasted the way they might be under a single annual cap. A market that lurches downward even once, though, can undo several months of capped upside in a single stroke.
The formula behind the credit
The math is a running total, not a single calculation. Each month's contribution depends on whether the index rose or fell:
Annual credit = the sum of each month's counted return
- A month with a gain counts up to the monthly cap and no further (for example, a month that gained more than a hypothetical 2.0% cap would only contribute 2.0%).
- A month with a loss, or no change, counts in full, with no cap applied.
Example: a calm, low-volatility year
Say a contract carries a hypothetical monthly cap of 2.0%, and the index climbs gently through the entire year without a single down month.
| Months | Index return | Counted return |
|---|---|---|
| Jan through Jun (6 months) | +1.2% each | +1.2% each |
| Jul through Nov (5 months) | +1.6% each | +1.6% each |
| Dec | +1.0% | +1.0% |
| Annual total | +17.2% | +16.2% |
Add it up: six months at 1.2% contribute 7.2%, five months at 1.6% contribute 8.0%, and December adds another 1.0%, for a credited total of 16.2%. None of those monthly figures crossed the 2.0% ceiling, so every bit of that gain counted. An annual point-to-point contract with a hypothetical 8.0% cap would have handed you only 8.0% in the same calendar year, because it measures the index just once.
Example: a year with one sharp drop
Now picture the opposite pattern: mostly solid months, but one bad one mixed in.
| Months | Index return | Counted return (2.0% cap) |
|---|---|---|
| 9 months | +3.0% each | +2.0% each (capped) |
| 1 month | -14.0% | -14.0% (no cap on losses) |
| 2 months | +2.5% each | +2.0% each (capped) |
| Raw index total for the year | +18.0% | |
| Credited total | +8.0% |
The raw index actually finished the year up 18.0%. But every gaining month got trimmed to 2.0%, while the single losing month subtracted its full 14.0% from the running total: nine months at 2.0% add up to 18.0%, the down month removes 14.0%, and the last two months add another 4.0%, leaving a credit of 8.0%. A hypothetical 8.0% annual point-to-point cap, applied to that same 18.0% raw gain, would have credited the full 8.0% too, in this case landing at roughly the same place, though a smaller down month or a smaller cap could easily have tipped the outcome either way.
When monthly sum tends to win
- A market that grinds higher in small steps. If most months land somewhere between a small positive return and the monthly cap, you capture nearly all of it, something a single annual cap would never allow.
- Long stretches with little volatility. Calm bull markets, where gains arrive steadily rather than in a few big jumps, are exactly the conditions this method rewards.
- A generous monthly cap. A higher monthly cap paired with a calm market can produce a very large annual credit on paper, though contracts offering the most generous monthly caps have become less common as rates have shifted.
When monthly sum tends to lose
- Choppy or volatile years. Any month that falls more than the size of your capped gains works against you, because losses are never capped the way gains are.
- A market that jumps in one big move. If most of the year's gain happens in a single strong month, you only keep the capped portion of that month and miss the rest.
- Sharp, sudden downturns. A market shock concentrated in one or two calendar months, the kind seen during past crashes, can wipe out a monthly sum credit for the entire year even when other months were solid.
Monthly sum versus annual point-to-point
The two methods reward different kinds of years. These outcomes are approximate and use hypothetical caps of 2.0% monthly and 8.0% annual to illustrate the pattern, not to predict actual results.
| Market pattern over the year | Monthly sum (2.0% cap) | Annual point-to-point (8.0% cap) |
|---|---|---|
| Index up 20%, in steady small steps | about 20% | 8% |
| Index up 8%, in steady small steps | about 8% | 8% (tie) |
| Index up 20%, with one sharp down month | about 8% | 8% (tie) |
| Index up 3%, with one sharp down month | 0% to 2% | about 3% |
| Index down for the year | 0% | 0% (tie) |
Monthly sum is, at its core, a bet that the ride will be smooth. Annual point-to-point is a bet that the year finishes positive, regardless of how bumpy the path was to get there. A choppy year tends to favor the annual measurement; a calm, grinding year tends to favor the monthly one.
Typical monthly cap ranges
Monthly caps vary by contract length, carrier strength and the interest rate environment, and they move often enough that we will not print a specific number here. In general, shorter contract terms and lower-rated carriers tend to sit at the lower end of the range, mid-length and longer contracts from strong carriers tend to cluster in the middle, and a handful of longer contracts with an upfront bonus occasionally reach the top end, though those have grown less common in recent years.
A useful shortcut: multiply any monthly cap by 12 to see its theoretical ceiling. A hypothetical 2.0% monthly cap caps out at 24.0% if every single month hit the ceiling, which almost never happens in practice once ordinary volatility is factored in. Get a quote to see the current monthly caps available for your state and deposit size.
Who fits monthly sum crediting
Monthly sum tends to suit buyers who expect the market to climb steadily without major drawdowns, who are comfortable earning zero in a year with one bad stretch, and who want a shot at outperforming an annual cap in the best-case scenario. It asks you to accept more downside asymmetry in exchange for that upside potential.
It is a weaker fit for a more conservative buyer who wants a smoother, more predictable credit every year. For most retirees prioritizing consistency over a shot at a bigger number, an annual point-to-point strategy or a participation rate strategy tends to produce more reliable results over a full contract term.
Related crediting methods
Frequently asked questions
How does monthly sum crediting actually work?
The carrier checks the index's change on each of your twelve monthly contract anniversaries. Each month that gained is trimmed down to a set ceiling before it counts, and each month that lost ground counts against the total exactly as it happened. Those twelve figures are added together at your contract anniversary. A positive sum becomes your credit for the year; a sum at zero or below simply pays nothing, and your principal is never touched either way.
How high do monthly caps typically run?
Most contracts fall somewhere between roughly 1.5% and 2.5% per month, with something close to 2.0% showing up most often on longer, 7 to 10 year terms from strong carriers. These figures move with interest rates and the broader market, so treat any number as a rough guide rather than a locked-in current rate.
Can this method beat a single annual cap?
It can, when conditions cooperate. A run of small, steady gains that each stay under the monthly ceiling can stack up to far more than a one-time annual cap would ever allow, since none of those months go to waste under a yearly limit. That same setup, though, leaves you fully exposed the moment one month drops hard.
In what kind of year does this method fall short?
Any stretch with a sharp monthly decline hurts monthly sum crediting more than most alternatives. Since a losing month is never trimmed the way a gaining month is, a single steep drop can cancel out several months of capped gains, leaving you with a small credit or none at all even in a year the index ultimately finished ahead.
Could a rough year actually cost me money?
No. Index performance can never pull your principal down under any fixed index annuity, monthly sum included. The floor in a difficult year is a credit of zero, regardless of how many negative months the index posted along the way.
Written and reviewed by
James Forren Warren
Licensed Retirement Income Strategist · License #20551202
James Forren Warren is a licensed Retirement Income Strategist with Tax Free Wealth Plan. For the past five years he has helped individuals and families turn their savings into retirement income they can count on. He writes and reviews the annuity research on this site and keeps it plain: what a product does, what it costs you, and who it actually fits.
Sources
Educational only, not investment, tax or legal advice. Tax Free Wealth Plan LLC is a licensed insurance agency, not a registered investment adviser or broker-dealer. Annuities are not bank deposits, are not FDIC insured and are not guaranteed by any government agency. Guarantees are backed solely by the claims-paying ability of the issuing insurance company. Features, rates and availability vary by state and change over time; the contract and disclosure documents govern.