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Installment Sales: How to Defer Exit Taxes Legally Over Multiple Years

Author: Yanni Papoutsi - Fractional VP of Finance and Strategy for early-stage startups - Author, Exit Ready Published: 2026-03-14 - Last updated: 2026-03-14

Reading time: ~12 min

The Tax Problem Without Installment Sales

When you sell a company, the tax bill is often the biggest shock. Imagine you build a business from $0 cost basis to a $100M sale. Your capital gain is $100M. At federal long-term capital gains rates (20% for gains over $500K) plus 3.8% Net Investment Income Tax, plus state taxes (assuming California's 13.3%), your total tax rate is roughly 37%. Your tax bill is $37M. You walk away with $63M.

But there is a worse problem: when you recognize $100M in gains in a single year, you are pushed deep into the highest federal tax bracket. The marginal tax rate on the last dollar of gain is 37% plus the 3.8% NIIT, totaling 40.8%. Your effective tax rate is even higher because top bracket income is subject to phase-out of deductions and preferences.

This is where IRC Section 453 installment sale treatment becomes valuable. Instead of recognizing all gains in the year of sale, you defer gain recognition to the years in which you receive payments. If you structure the sale as $40M at closing, $30M in year 2, $30M in year 3, you recognize gains across three years. This keeps your marginal rate lower and potentially saves you substantial taxes.

How Installment Sales Work Under IRC Section 453

The mechanics are straightforward. You sell your business for $100M. Your cost basis is $20M. Total gain is $80M. The gain percentage is 80% ($80M / $100M).

Payment schedule: $40M at closing (year 1), $30M at closing of year 2, $30M at closing of year 3.

Year 1: You receive $40M. Your recognized gain is 80% of $40M = $32M. Return of basis is 20% of $40M = $8M.

Year 2: You receive $30M. Your recognized gain is 80% of $30M = $24M. Return of basis is 20% of $30M = $6M.

Year 3: You receive $30M. Your recognized gain is 80% of $30M = $24M. Return of basis is 20% of $30M = $6M.

Total recognized gains: $32M + $24M + $24M = $80M (correct).

Tax liability (assuming 37% total rate): Year 1, $11.84M. Year 2, $8.88M. Year 3, $8.88M. Total tax bill = $29.6M.

Compare this to recognizing all gains in year 1 ($37M tax). The deferral saves $7.4M in taxes.

The key advantage is that you are not pushed into the top tax bracket in any single year. Your taxable income is spread, so you may remain in the 20% long-term capital gains bracket for portions of the gain. If the deferral pushes some gains into lower tax years (e.g., a year with lower income from other sources), the tax savings increase further.

The Interest Component: Imputed Interest and AFR

There is a cost to installment sale deferral: the IRS imposes a minimum interest rate on the deferred payment, called the Applicable Federal Rate (AFR). As of March 2026, short-term AFR is roughly 5.3%, mid-term AFR is 5.0%, and long-term AFR is 5.2%.

If your buyer gives you a promissory note for $60M (deferred payments over 3 years), the note must include at least 5% annual interest, compounded. The interest is ordinary income, taxed at your marginal rate (roughly 40% federal + state), so the effective cost of the deferral is interest paid plus taxes on that interest.

In the example above, the $30M payment in year 2 is not just $30M; it includes interest on the deferred $30M from year 1. Interest accrues and compounds. The actual interest obligation might be $1.5M-$2M on the year 1 deferral. You pay this out of your cash flow or request that the buyer increase the principal payment to cover interest.

The math still works in your favor: savings on capital gains tax ($7.4M in the example) exceeds the cost of interest ($3-4M on $60M deferred). But the interest is a real cost that must be factored into the deal economics.

Best practice: Structure the deal so that the buyer pays all interest and the deferred principal to you. If the buyer is paying $30M in year 2, that should include accrued interest. You do not want to pay interest out of your proceeds.

The Promissory Note: Mechanics and Security

An installment sale requires a formal promissory note executed by the buyer. The note specifies:

- Principal amount: The portion of purchase price being deferred.
- Maturity date: When the note is due (e.g., 3 years from closing).
- Interest rate: Must be at least the IRS AFR rate (5%+ depending on term). The rate can be higher (e.g., 7% if the buyer is willing).
- Payment schedule: Monthly, quarterly, or annually as agreed.
- Security: Is the note secured by a lien on the company's assets, a guarantee from the buyer's parent company, or unsecured (riskier)?

Security is critical. If the buyer defaults on the promissory note, you need recourse. Best practice: Secure the note with a first lien on all assets of the company or a personal guarantee from the buyer's principal shareholders or parent company.

In M&A deals, buyers rarely give seller notes with first lien security (they have given liens to their debt lenders). Instead, seller notes are typically subordinated to debt or unsecured. This increases your risk. If the buyer encounters financial distress, debt lenders get paid first, and your seller note may be worthless. Mitigation: (1) Require a personal guarantee from the buyer's principals or parent company. (2) Require that the buyer maintain certain financial covenants (minimum cash, maximum debt, etc.). (3) Request that the buyer maintain key person insurance, naming you as a beneficiary. (4) Require that proceeds from the deferred payment escrow (often 10-15% of purchase price is held in escrow for purchase price adjustments) flow to the seller note if not used for adjustments.

Installment Sales vs. Earnouts: Key Differences

Many M&A deals include earnouts: the buyer pays the headline price plus contingent amounts based on future revenue or EBITDA. Earnouts are a form of deferred payment and may qualify for installment sale treatment, but the mechanics differ.

Promissory note (seller note):

- Amount is fixed ($30M deferred payment, certain).
- Interest accrues on the fixed amount.
- Payment schedule is predetermined.
- Risk: Buyer default on payment obligation.
- Tax treatment: Installment sale treatment applies; gains are recognized pro-rata as payments are received.

Earnout:

- Amount is contingent on future performance ($5-10M based on revenue hitting targets).
- No interest accrues; the earnout is additional purchase price, not debt.
- Payment depends on actual business performance post-close.
- Risk: Business underperforms, earnout is not paid (but this is not buyer default; it is a performance miss).
- Tax treatment: The earnout is treated as contingent consideration. Gains are recognized when the earnout is paid or becomes probable (complex rules; consult your tax advisor).

For tax deferral purposes, a fixed promissory note is superior to an earnout because you know the payment timeline and can calculate the installment gain percentage with certainty. Earnouts are riskier because you depend on the buyer actually executing the business plan.

Deal Structure: Asset Sale vs. Stock Sale

Installment sale treatment applies primarily to asset sales. If you are selling your company's assets (goodwill, IP, customer relationships, physical assets), the buyer is purchasing those assets, and a promissory note for deferred payment qualifies for installment treatment. Learn more about structuring your exit for maximum tax efficiency in Exit Ready.

Stock sales are more complicated. If your company is a C corporation and you are selling stock, installment sale treatment is generally not available because Section 453 applies to sales of property, and there are exceptions for stock. If your company is an S corp or LLC taxed as a partnership, installment sales can still apply to the asset sale economic equivalent of the stock sale.

For founders, this means: If possible, structure the sale as an asset sale and take an installment note. Your tax advisor can help navigate the mechanics, but asset sales are more installment-sale-friendly than stock sales.

Combining Installment Sales with QSBS Exclusion

If you have Qualified Small Business Stock (QSBS)—stock you have held 5+ years in a qualifying C corporation—you may exclude up to 100% of gains on the sale, capped at the greater of $10M or 10x cost basis. This is an extraordinary tax provision and should be the primary goal of exit planning.

If your company qualifies for QSBS and you sell all the stock for cash at closing, the entire gain is excluded from federal income tax. No installment sale is needed because there is no tax deferral needed (no tax period).

However, many sales do not qualify for QSBS due to company age, timeline, or other factors. For those situations, installment sales are the secondary tax strategy. Additionally, if part of your holding is QSBS-eligible and part is not, you can exclude the QSBS gains and use installment sale treatment for the non-QSBS gains.

Example: You have $100M in total gains. $80M qualifies for QSBS exclusion. $20M does not. You exclude the $80M and use installment sale treatment for the $20M. The installment sale treatment allows you to spread the $20M across multiple years, saving on the marginal tax rate applied to that portion.

Real-World Scenario: Leveraging Installment Sales

A founder sold a software company to a strategic buyer for $50M. The all-cash deal would have created a $45M capital gain (assuming $5M basis). The founder's tax liability would have been roughly $16.65M federal and state (37% rate), leaving $33.35M net.

Instead, the founder negotiated a deferred deal: $20M at closing, $15M in year 2, $15M in year 3. The promissory note was secured by a personal guarantee from the buyer's CFO and an escrow holdback for representations and warranties.

Tax recognition: Year 1, $18M gain (80% × $20M). Year 2, $13.5M gain. Year 3, $13.5M gain. Total $45M (correct).

Tax liability: Year 1, $6.66M (37% × $18M). Year 2, $5M (37% × $13.5M). Year 3, $5M. Total tax liability = $16.66M (same as all-cash).

But the key benefit emerged: In year 2, the founder had lower income from other sources (salary ended, investment income was low). The marginal rate on the $13.5M gain was 24% (state + fed), not 37%. This saved ~$1.75M in year 2. In year 3, similar dynamics applied. Total tax savings: $3.5M across the deferral.

Additionally, the founder benefited from investing the deferred payment amounts. The $15M in year 2 and year 3 were invested conservatively; the compounding value and flexibility in tax timing added another $2-3M in value.

Total benefit: $3.5M in tax deferral + $2.5M in investment timing = $6M in value creation through installment sales structuring.

Risks and Limitations

Installment sales are not free. Risks include:

- Buyer credit risk: If the buyer fails to pay, you are an unsecured creditor (or a subordinated creditor). You may recover only a portion of the deferred amount in bankruptcy.
- Interest rate risk: If interest rates fall, the AFR rate you are locked into may be above market, and the deferred payments become less competitive.
- Inflation risk: If inflation rises, the deferred payment dollars are worth less in purchasing power (though the gain is still recognized for tax purposes).
- Complexity: Installment sales require careful documentation and accounting. The interest must be properly accrued and accounted for each year. Failure to do so can result in IRS penalties.
- Section 453 repeal risk: Congress has periodically discussed repealing Section 453. While this is unlikely, it is a future legislative risk.
- Market timing: If you are deferring payment into a rising market and interest rates rise, the deferred payments may become less attractive relative to receiving cash immediately and investing it.

Tax Advisor Coordination

Installment sales require close coordination with your CPA and tax counsel. Your advisors should:

- Review the deal structure and promissory note to ensure installment sale treatment is available and properly documented.
- Calculate the gain percentage and ensure it is properly reported on Form 6252 each year.
- Coordinate with your M&A advisors on deal terms to optimize both economic and tax outcomes.
- Model the tax impact across multiple years and scenarios (e.g., if interest rates rise, buyer defaults, etc.).
- Ensure the promissory note includes proper interest at the IRS AFR minimum rate and includes all required terms.