Buried inside a 1974 IRS revenue ruling is a math problem most retirement plan participants will never see. But if you’re a high-earning business owner using a cash balance plan, it might quietly determine whether that plan stays qualified or blows up in an audit.
It has a name only a tax attorney could love: the 50% rule. And the calculation behind it has an even worse name: individual level premium funding. Stick with me anyway.
This article breaks down exactly how the 50% rule works in a cash balance context, what the “theoretical contribution” really is, and how the individual level premium funding method actually computes it. Just the real mechanics, in plain English, with a worked example you can actually follow!
Why this rule exists
The IRS lets you put life insurance inside a qualified retirement plan, but they don’t want people turning a “retirement plan” into a “life insurance plan with a tiny retirement bolt-on.” So they say: insurance has to be incidental — a side dish, not the main course. The 50% rule from Rev. Rul. 74-307 is one of the ways the IRS measures “incidental.”
The easy version (profit-sharing / money purchase plan)
In a regular defined contribution plan, the rule is straightforward because there’s an actual dollar contribution going into your account each year. The rule basically says: less than 50% of the employer money going into your account can be used to pay whole life insurance premiums (and less than 25% if it’s term or universal life). If your employer puts $20,000 into your account, less than $10,000 of that can pay whole life premiums. Easy.
The problem with cash balance and other defined benefit plans
Cash balance plans don’t really work that way. There’s no “contribution credited to your account.” Instead, the plan promises you a benefit at retirement, and the actuary figures out what the company needs to put in overall to fund those promises. So if the rule says “less than 50% of the contribution credited to the participant,” there’s no obvious number to plug in.
The IRS knew this, so they bolted on a workaround. Pretend there was a contribution just for that one person, and use that pretend number as the denominator. That pretend number is called the theoretical contribution. The way you calculate it is the “individual level premium funding method.”
Individual level premium funding — what it actually means
“Individual level premium” sounds fancy but it’s simple. It’s just asking: what flat, level annual amount, paid every year from the day this person entered the plan until their normal retirement age, would be enough to fund their promised retirement benefit? Same dollar amount every year, like a mortgage payment in reverse.
Three ingredients go into that calculation:
- The participant’s entry age (when they joined the plan)
- The participant’s normal retirement age (usually 62 or 65)
- The promised retirement benefit, valued using reasonable interest and mortality assumptions stated in the plan document
A super simple example
Let’s say Dr. Smith joins a cash balance plan at age 50, normal retirement age is 65, so there is a 15 year funding runway. The actuary says the promised benefit at 65 is worth, in today’s dollars, a lump sum that would require a level annual deposit of $80,000 per year for 15 years to fully fund (using the plan’s assumed interest rate and mortality table).
That $80,000 is the theoretical contribution. That’s the denominator.
Now apply the 50% test. If the plan wants to buy a whole life policy, the annual premium has to be less than 50% of $80,000 = less than $40,000 per year. If it’s term or universal life, less than 25% = less than $20,000 per year. Stay under that line and the insurance is “incidental.” Cross it and the plan has a qualification problem.
One wrinkle worth knowing
You’ll see some sources say “two-thirds / one-third” instead of “50% / 25%” for DB plans. That’s not a contradiction. It’s an alternative path in the same ruling (sometimes called the “reserve method”).
Under this method, you can push premiums up to 66% for whole life as long as the death benefit is capped at face amount + theoretical reserve – cash value. Different test, different limit, but same ruling. But the headline 50%/25% rule is the one most people mean when they say “the 50% rule.”
That’s the whole thing. The trick is really just that cash balance plans don’t have a real contribution to test against. So the IRS invented one (the theoretical contribution), and the way you build that invented number is the individual level premium funding method — a flat annual amount that would fund the promised benefit from entry age to retirement age.
Bottom Line
The 50% rule isn’t really complicated once you see what the IRS is doing. They wanted a way to test “incidental” insurance in plans that don’t have account-level contributions, so they invented one — the theoretical contribution — and used the individual level premium funding method to size it. Once that translation is in place, the test works the same way it would in any profit-sharing plan: less than 50% of the number for whole life, less than 25% for term or universal life. That’s the whole game.
If you’re a business owner thinking about life insurance inside a cash balance plan, three things should happen before any policy is written. Your actuary should compute the theoretical contribution using the funding method and assumptions specified in your plan document. Your plan document should explicitly authorize life insurance and spell out the funding source. And your premium should be checked against the ceiling every year — not just on day one.
Get this right and you can stack meaningful death benefit on top of an already powerful retirement vehicle without putting the qualification at risk. The 50% rule isn’t there to trip you up — it’s there to make sure your retirement plan stays a retirement plan.
