Rule of 78s
What is Rule of 78s, and is it illegal?
Rule of 78s is a method some precomputed-interest loans use to front-load how much of the total finance charge counts as "earned" in the early months, so paying off early returns less interest than a straight day-by-day split would. It is not banned everywhere, despite a common claim — federal law bans it only on consumer loans with terms longer than 61 months, and some states add further restrictions on shorter contracts too.
Key takeaways
- Rule of 78s is a formula for front-loading interest recognition within a precomputed-interest loan — it is not a separate type of loan on its own.
- The name comes from a standard 12-month loan: adding the digits 1 through 12 equals 78, the denominator used to weight each month's share of the total interest.
- It is not banned everywhere. Federal law bans Rule of 78s only on consumer loans with terms longer than 61 months, roughly 5 years and up.
- Some states impose their own additional restrictions or outright bans on Rule of 78s for shorter-term loans too — the rules vary by state, so the contract and state law both matter.
- It can still legally appear on some shorter-term subprime and buy-here-pay-here contracts, which is exactly why telling 'simple interest,' 'precomputed,' and 'Rule of 78s' apart matters.
What is Rule of 78s?
Rule of 78s is a formula for dividing up the interest on a precomputed-interest loan, so that more of it counts as "earned" by the lender in the early months of the term than in the later months. It only applies inside a precomputed schedule — it is not a loan type of its own, and it has nothing to do with simple-interest loans, where interest just accrues daily on the balance.
The practical effect is that if you pay off a Rule of 78s loan early, you get back less unearned interest than a straight, even split across the months would suggest.
Why is it called "Rule of 78s"?
The name comes from arithmetic on a standard 12-month loan. Adding the digits 1 through 12 gives 78, and that sum becomes the denominator used to weight each month's slice of the total interest — month 1 gets 12/78 of the interest, month 2 gets 11/78, and so on down to month 12's 1/78. Earlier months are weighted more heavily even though the loan balance declines the same way it would under simple interest.
For loans of other lengths, the same idea applies using that term's digit sum instead of 78, but the shorthand name stuck regardless of the actual term.
Is Rule of 78s banned?
Only partly, and getting the scope right matters. A widely repeated claim online says Rule of 78s is banned everywhere — that is not accurate.
| Claim | Accurate? |
|---|---|
| "Rule of 78s is banned everywhere" | No. Federal law bans it only on consumer loans with terms longer than 61 months. |
| "It's banned on every short-term loan too" | Not universally. Some states add their own bans or limits on shorter-term Rule of 78s contracts; others don't. |
| "It can still legally appear on some contracts today" | Yes — mainly on shorter-term subprime and buy-here-pay-here paper, where state law permits it. |
Federal law restricts Rule of 78s specifically on consumer loans with terms longer than 61 months — that is, longer than about 5 years. Below that threshold, whether it is allowed depends on state law, which varies: some states restrict or ban Rule of 78s on shorter consumer loans too, while others permit it. Because auto loans are commonly written for 60, 72, or 84 months, plenty of contracts fall on either side of that federal line, which is exactly why the term still turns up in real financing paperwork.
How does this actually affect an early payoff?
The finance charge on the loan was fixed at signing, same as any precomputed loan. What Rule of 78s adds on top is an uneven split of that fixed charge across the months, weighted toward the start. So a borrower who pays off in month 6 of a 12-month Rule of 78s loan gets back noticeably less than half the total interest, even though half the calendar term is left.
That is a materially worse outcome for early payoff than either a simple-interest loan (where the daily calculation naturally favors an early payoff) or even a precomputed loan without the Rule of 78s weighting (where the finance charge is spread more evenly). If your contract references Rule of 78s, ask for a written payoff quote before assuming what an early payoff is actually worth.
What to check on your own contract
Search your retail installment contract for the phrase "Rule of 78s," "sum of the digits," or "precomputed." If any of those appear, or if the servicer confirms the loan is precomputed, ask specifically how early-payoff rebates are calculated rather than assuming a simple pro-rata refund. See precomputed interest for the broader category this method sits inside.
Common questions
Is Rule of 78s illegal?
Not universally. Federal law bans its use only on consumer loans with terms longer than 61 months. On shorter loans it can still legally appear on some contracts, though a number of states impose their own additional restrictions, so state law and your own contract both matter.
Why is it called Rule of 78s?
It comes from the math on a standard 12-month loan: adding the digits 1 through 12 equals 78. That sum becomes the denominator used to weight how much interest counts as earned each month, with earlier months carrying a larger share.
How does Rule of 78s affect an early payoff?
It front-loads interest recognition, so more of the total finance charge counts as already earned by the lender in the early months. Paying off early returns less unearned interest than a simple day-by-day interest calculation on the same loan would.
Is Rule of 78s the same as precomputed interest?
No. Precomputed interest is the broader category — a total finance charge fixed at signing. Rule of 78s is one specific method some precomputed contracts use to spread that fixed charge unevenly across the term, weighted toward the early months.
Where does Rule of 78s still show up today?
Mostly on shorter-term subprime and buy-here-pay-here contracts, where it remains legal in many states. It is less common on mainstream bank, credit union, and captive-lender financing, which typically use simple interest instead.