IRC §453A Interest Charge: The $5 Million Rule, the Rate, and a Worked Example

The §453A formula

The underpayment rate for October to December 2026 is 7% (IRS quarterly interest rates), so a calendar-year taxpayer uses 7% for 2026. The charge recurs every year the obligation is outstanding, recomputed on the unrecognized gain still left.

Go deeper: the Section 453A interest charge on installment notes over $5 million on Big Sale Tax.

Worked example: a $12 million business sale

A seller closes a $12,000,000 sale of a business (all long-term capital gain, $2,000,000 basis) in 2026, taking $2,000,000 at closing and a $10,000,000 note.

Against the time value of deferring roughly $1.67 million of federal tax (and state tax on top), that charge is usually worth paying, but it has to be in the model. As principal is paid down, the unrecognized gain shrinks and so does the charge; the applicable percentage stays fixed for obligations from that year. Illustrative only; your CPA computes the actual figure on your return.

How the charge works

A structured installment sale under IRC §453 lets you spread the tax on a big gain across the years you're paid. On large sales, a second rule attaches a cost to that deferral: the §453A interest charge.

Most §453 illustrations never mention it. On a $10M business or commercial-property sale it can take real money off the benefit. On a $3M home sale it doesn't apply at all, at any size. Know which side of that line your deal is on before you sign.

What §453A actually does

§453 is the default installment method: you recognize gain, and pay tax, only as payments arrive. §453A doesn't undo that. It says that on large deferrals, the IRS charges you interest on the tax you haven't paid yet. In effect, the government treats your deferred tax like a loan and bills interest on it each year until it's paid.

It applies only to nondealer installment obligations: the ordinary business owner or property seller, not a dealer flipping inventory.

When §453A applies

Three conditions have to line up:

1. The sale price exceeds $150,000. Small sales are exempt outright.
2. The face amount of installment obligations that arose during the tax year and are still outstanding at its close exceeds $5,000,000. This is an aggregate test of that year's notes, measured at year-end. Once a year's obligations meet it, they stay subject to the charge in every later year they are outstanding.
3. The obligation is still outstanding at year-end. As you're paid down and the balance drops, the charge shrinks with it.

If all three are true, §453A imposes an annual interest charge on the applicable percentage of your deferred tax liability. The rate is the IRS underpayment rate under §6621(a)(2) for the last month of your tax year, so the cost floats with prevailing rates. Only the share of the deferred tax attributable to obligations above $5 million is charged; the first $5 million of face amount rides free.

Put simply, it's a yearly interest bill on the portion of your deferred tax that sits on installment balances over $5 million. On a large commercial or business sale, that's a real line item to model. It won't kill the deal, but you don't want to find it after closing.

When §453A does NOT apply

Most sellers, and a surprising number of advisors, get this part wrong. §453A carves out entire categories:

• Personal-use property, including your primary residence. The sale of a personal residence is not subject to the §453A interest charge, regardless of the size of the outstanding note. A homeowner sitting on a $2M, $5M, or larger gain over the §121 exclusion can structure the entire gain under §453 with no §453A ceiling and no interest charge. No other §453 case is this clean.
• Farm property. Property used or produced in the trade or business of farming is likewise excluded.
• Any year your aggregate installment obligations stay at or under $5,000,000. Structure a larger sale so the deferred face stays under the threshold (a partial cash-out, a partial 1031, or a shorter deferred portion) and §453A never attaches.

That first bullet is why a long-held California home is the most favorable structured-sale case in the country. Bought decades ago, worth several million now, a gain far past the $500,000 married exclusion. And §453A, the one rule that can drag on a large deferral, is switched off by statute.

The pledge rule: don't borrow against the note

§453A carries a companion rule under §453A(d): if you pledge or borrow against the installment obligation, the loan is treated as a payment and accelerates your gain. You're taxed as if you'd cashed out to the extent of the borrowing. A §453 stream is income you're scheduled to receive, not collateral. Using it as loan security defeats the deferral.

The pledge rule has a lower trigger than the interest charge: it applies to any nondealer installment obligation from a sale over $150,000, whether or not the $5 million test is met. The personal-use and farm property exceptions apply to it as well.

What this means for structuring your sale

None of this means avoid large deals. A large commercial or business sale needs the §453A charge modeled honestly up front. A residence sale never does. Any §453 illustration on a multimillion-dollar commercial gain that doesn't show the §453A line is showing you a number you'll never actually see.

This is educational information about how IRC §453A operates, not tax or legal advice. Your outcome depends on your basis, the property type, your aggregate obligations, and prevailing §6621 rates. Model every deal against its own facts with your own CPA before you commit.

Run your number before you sign

If your sale is over $5 million, model the §453A charge to the dollar. If it's a home, you'll want to see how clean the structure is with the charge switched off. Send the sale price, your basis, and the property type, and I'll run it both ways in 24 hours.

Frequently asked

Q: What is the §453A interest rate for 2026? A: The IRS underpayment rate under §6621(a)(2) for the month your tax year ends. For a calendar-year taxpayer that is the October to December 2026 rate, which the IRS set at 7%.

Q: How is 453A interest calculated? A: Multiply the unrecognized gain on the obligation at year-end by the maximum tax rate (20% for long-term capital gain) to get the deferred tax liability. Multiply that by the applicable percentage, which is the face amount above $5 million divided by the total face amount outstanding. Multiply the result by the underpayment rate.

Q: Does §453A apply to the sale of a primary residence? A: No. Obligations from an individual's sale of personal use property, which includes a personal residence, are excluded under §453A(b)(3)(A), as is property used or produced in farming.

Q: Does the $5 million threshold apply per sale or in total? A: In total. It is the face amount of all installment obligations that arose during the tax year and are outstanding at its close. Two $3 million notes from the same year total $6 million and are over the threshold.

Q: What is the §453A pledge rule? A: Under §453A(d), if you borrow against an installment obligation from a sale over $150,000, the net loan proceeds are treated as a payment on the note, which accelerates gain. It applies even when the $5 million interest-charge test is not met.

Sources: 26 U.S.C. §453A (Cornell LII), IRS quarterly interest rates, IRS Publication 537, Installment Sales.

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