Simple Interest Is a Silent Wealth Destroyer

You lend someone $15M at 6%. They pay interest every year. The principal sits untouched. After five years, you've earned $4.5M in interest.

Under compound interest, you'd have earned $5.1M — and every unpaid year would have made the next one more expensive for the borrower. Simple interest gives you less money and removes the borrower's incentive to pay you back. One word in the loan agreement. Two consequences.

Simple interest on seller notes is one of the quietest wealth transfers in PE deals. It doesn't look aggressive. It doesn't sound unfair. It just costs you money every year the principal goes unpaid.

The Unplugged Meter

Think of a parking meter that charges a flat fee per day, regardless of how long you stay. Park for one hour or park for twelve — same charge. There's no escalating penalty. No reason to move the car.

Compound interest is the meter that ticks faster the longer you stay. It creates urgency for the borrower. Every day the debt sits, the cost of holding it increases. The borrower has an economic incentive to pay it off.

Simple interest is the flat-fee meter. The cost of carrying the debt is the same on day one as it is on day one thousand. The borrower can park on your money indefinitely. The penalty never escalates.

The Math Nobody Runs

The Crossfield seller notes carried 6% simple interest on $15M. The math looks clean: $900K per year in interest. Ridgeline pays the interest. The principal waits.

Here's what the founders didn't model.

Under simple interest, the $900K in Year 1 is worth $900K. The $900K in Year 5 is also worth $900K. But adjusted for inflation and the time value of money, that Year 5 payment buys less. The real value of the interest stream erodes every year. The founders lose purchasing power on money they already earned.

Under compound interest, unpaid interest gets added to the principal. The balance grows. Year 1 interest on $15M at 6% is $900K. If unpaid, Year 2 interest is calculated on $15.9M. By Year 5, the balance has grown to over $20M. The buyer's cost of delay increases every year. That's the incentive to pay.

With simple interest, the buyer's cost of delay is flat. Ridgeline can hold the $15M for five years or ten years. The annual carrying cost never changes. There is no economic trigger that forces repayment. No compounding penalty. No accelerating urgency.

The founders negotiated the interest rate. They didn't negotiate the interest structure. That single word — simple instead of compound — gave the buyer a fixed-cost loan on the sellers' money with no urgency to repay it.

Ridgeline's financial team understood this. Simple interest meant they could deploy the $15M in acquisitions and earn returns well above 6%. The founders' money funded the buyer's growth strategy at a fixed rate with no escalation.

Deal Spectrum: 9/10

The left column shows what a founder-favorable version of this term looks like. The right column shows what Crossfield signed.

The mental model is the Silent Wealth Destroyer. Simple interest doesn't look punitive. It doesn't feel aggressive. It quietly transfers value from seller to buyer every year the principal sits unpaid. Not through a visible mechanism. Through one the seller never modeled.

The Crossfield Moment

Fourteen months post-close, Dan's accountant ran the numbers on the seller notes. Interest payments were current. Principal was untouched. Dan asked the obvious question: when does Ridgeline have to pay the $15M back?

The accountant pointed to the note terms. No mandatory amortization schedule. No maturity acceleration trigger. No compounding.

"They can hold this for a decade and it costs them exactly what it costs them today."

Dan stared at the spreadsheet. Six percent of $15M, flat, forever. A line that never curves upward.

Founder Protection Tips

Negotiate compound interest — unpaid interest should accrue to the principal. This is the single most important structural protection on any seller note.

Negotiate mandatory amortization starting no later than 12–24 months post-close. If the buyer isn't making principal payments on a schedule, they're using your money rent-free.

Include strong default provisions — acceleration rights, penalties, and corporate guarantees. Without them, the buyer's cost of non-payment is zero.

Negotiate shorter maturity — 3–5 years maximum, with a meaningful step-up in rate if extended. The longer the note runs, the more value you lose.

Read before you sign.