Section 453A(c) Interest Charge: Calculation, Pledging, and Reporting

The Section 453A interest charge calculation is a three-factor multiplication: your deferred tax liability, times the applicable percentage, times the IRS underpayment rate in effect when your tax year ends. Before you run those numbers, confirm both statutory gates are open. The individual installment sale price must exceed $150,000, and the total face amount of your qualifying installment obligations arising that year and still outstanding at year-end must exceed $5 million.¹²

Confirm Both Thresholds Apply

Section 453A does not touch installment sales at or below $150,000, regardless of how many of them you have.¹ Even when a sale clears that per-sale gate, the interest charge only activates if the aggregate face amount of qualifying obligations arising in the same tax year and outstanding at year-end tops $5 million.² A single $3 million note clears the first bar but not the second, and no charge applies.

The $5 million figure is not just a switch. It also feeds the applicable percentage, which measures the portion of your deferred tax that sits above the floor. A taxpayer holding $6 million in qualifying obligations pays the charge on the excess, not on the full amount.

Aggregation and Exclusions

For partnerships and S corporations, the $5 million test happens at the partner or shareholder level, not the entity level. The entity allocates each owner’s share, and each owner combines those with any other qualifying obligations they hold. Related parties treated as a single employer under Section 52(a) or 52(b) also count as one person for threshold purposes, which prevents splitting a large sale across affiliated entities.³

Two categories of obligations are excluded entirely and do not count toward the $5 million floor:

Installment sales of personal-use property by an individual, such as a primary residence or personal vehicle.³
Property used or produced in a farming trade or business.³

If you sell a farm for $4 million and a commercial property for $3 million on installment in the same year, only the $3 million commercial obligation enters the calculation, and the aggregate test fails.

Step 1: Deferred Tax Liability

The deferred tax liability is what you would owe if you had to recognize all remaining gain right now. Compute it in two moves.

First, find the unrecognized gain at year-end. Take total gain on the sale, subtract gain already recognized from payments received, and the remainder is your unrecognized gain. Say you sold property for $10,000,000 with an adjusted basis of $4,000,000. Total gain is $6,000,000 and your gross profit ratio is 60%. A $2,000,000 down payment produces $1,200,000 of recognized gain, leaving $4,800,000 unrecognized.

Second, multiply that unrecognized gain by the maximum statutory rate. For individuals, the rate is 37% under Section 1. For corporations, the rate is 21% under Section 11.³ The statute uses the highest rate regardless of your actual marginal bracket, so the charge can overstate the real time-value benefit for lower-income taxpayers. In the running example: $4,800,000 × 37% = $1,776,000.

Step 2: Applicable Percentage

The applicable percentage isolates the slice of the deferred tax liability that sits above the $5 million floor. Take the aggregate face amount of applicable obligations arising in the tax year and outstanding at year-end, subtract $5 million, and divide by that same outstanding face amount.³

With one $8,000,000 note fully outstanding at year-end, the applicable percentage is ($8,000,000 − $5,000,000) ÷ $8,000,000 = 37.5%.

Recalculate this every year the obligation remains outstanding. As payments come in and the outstanding face amount drops, the ratio shifts. When the outstanding balance falls below $5 million, the numerator goes negative, which means the applicable percentage is zero and the charge phases out for that year.

Two mistakes are common here. The first is freezing the Year 1 percentage and reusing it; both terms in the fraction change annually. The second is aggregating obligations across years. The $5 million test applies separately to obligations arising in each tax year. A $4 million obligation from Year 1 and a $3 million obligation from Year 2 each fall below the floor on their own, and neither triggers the charge, even though the combined outstanding total is $7 million.

Step 3: Underpayment Rate

The third factor is the IRS underpayment rate under Section 6621(a)(2), which equals the federal short-term rate plus three percentage points.⁴ The statute specifies the rate in effect for the month in which or with which your taxable year ends.³ Calendar-year taxpayers use the December rate.

The IRS updates the rate quarterly. For the first quarter of 2026, the underpayment rate is 7%.⁵ Verify the rate for the quarter that includes your year-end month before you multiply; using the wrong quarter’s rate produces the wrong charge.

Full Example

Putting all three factors together for the sale above:

Sale price: $10,000,000
Adjusted basis: $4,000,000
Total gain: $6,000,000 (gross profit ratio 60%)
Down payment: $2,000,000
Gain recognized in year of sale: $1,200,000
Unrecognized gain at year-end: $4,800,000
Deferred tax liability: $4,800,000 × 37% = $1,776,000
Outstanding face amount at year-end: $8,000,000
Applicable percentage: ($8,000,000 − $5,000,000) ÷ $8,000,000 = 37.5%
Underpayment rate: 7%
Section 453A interest charge: $1,776,000 × 37.5% × 7% = $46,620

That amount is added to your income tax liability for the year. Run the whole calculation again next year with updated figures for unrecognized gain, outstanding face amount, and the current underpayment rate.

How Pledging the Note Changes the Number

Section 453A(d) can shrink or eliminate the charge by accelerating gain recognition. If you pledge an installment obligation as collateral for a loan, the net loan proceeds are treated as a payment on the note, and you recognize gain immediately on that deemed payment even though the buyer paid you nothing more.³ The deemed payment equals the lesser of the net loan proceeds or the remaining contract price minus payments already received.

The effect on the charge is mechanical. Recognizing gain shrinks the unrecognized gain, which shrinks the deferred tax liability, which shrinks the interest charge. Pledge the entire note and no deferred tax liability survives to be charged. Subsequent actual payments are not taxed again until they exceed the amount previously treated as paid.

The “secured indebtedness” definition is broad enough to catch indirect arrangements, including any deal that lets you satisfy the loan by handing over the installment note.³ A formal pledge is not required.

Reporting and Payment

The underlying installment sale is reported on Form 6252 each year you have payments or unrecognized gain.⁶ The Section 453A(c) charge is a separate computation, often presented on Form 8697 or an attached worksheet, with the resulting dollar amount carried to the appropriate line of Form 1040, 1120, or 1041.

The charge increases your tax for the year and is due by the original filing deadline, typically April 15 for individual calendar-year filers. An extension of time to file does not extend the time to pay, so an unpaid charge accrues additional penalties and interest.

The Charge Is Not Deductible for Individuals

The statute says the charge “shall be taken into account in computing the amount of any deduction allowable to the taxpayer for interest paid or accrued.”³ That reads like a promise of deductibility, and it is not. Treasury Regulation 1.163-9T(b)(2)(i)(A) treats interest on a federal income tax underpayment as personal interest, and Section 163(h) disallows personal interest deductions. The IRS treats the 453A(c) charge as falling into this category, making it nondeductible for individuals regardless of whether the underlying property was business or investment property.²

Factor the full, non-deductible cost into any comparison between electing out of the installment method and paying tax now versus deferring gain and paying the annual charge. On a large obligation held for years, the compounded non-deductible cost can meaningfully offset the benefit of deferral.

1
GovInfo. 26 USC 453A – Special Rules for Nondealers
2
Internal Revenue Service. Interest on Deferred Tax Liability
3
Office of the Law Revision Counsel. 26 US Code 453A – Special Rules for Nondealers
4
Internal Revenue Service. Revenue Ruling 2024-25
5
Internal Revenue Service. Interest Rates Remain the Same for the First Quarter of 2026
6
Internal Revenue Service. Topic No. 705 Installment Sales