Cross-border M&A in Japan regularly surfaces a fundamental disagreement between buyer and seller: what is the business actually worth today, and what will it be worth once the deal closes and integration begins? Earn-out arrangements, locked-box pricing, and completion accounts are the three primary contractual tools practitioners use to bridge that gap, allocate post-closing risk, and bring transactions to a signed definitive agreement when a single upfront number cannot satisfy both sides. Each mechanism carries distinct legal, accounting, and enforcement implications under Japanese law, and choosing the wrong one for a given deal can create disputes that consume the value the deal was meant to create. This article sets out how each mechanism works in a Japan M&A context, the drafting points that matter most, and the practical guidance a foreign buyer or seller needs to navigate the choice.
Last Updated: May 2026 · Reading Time: ~12 min
Why Earn-Outs Arise in Japan M&A
The Valuation Gap Problem
Valuation disagreements are not unique to Japan, but the Japanese market presents several features that make them particularly acute. Many targets are founder-owned businesses where the owner has operated informally, where revenue is concentrated in a handful of long-standing customer relationships, and where profitability projections depend heavily on the founder's continued involvement and the continuity of those relationships. A buyer looking at the business from the outside assigns a discount for those dependencies. The seller, who built the relationships and expects them to hold, assigns a premium.
The result is a gap that neither party can easily close through negotiation alone. The seller will not accept a price that treats the customer relationships as fragile. The buyer will not pay for revenue that may not materialize after the founder steps back. An earn-out defers a portion of the consideration and ties its payment to whether the business performs according to the seller's projections. If the projections are correct, the seller receives the full value they expected. If they are wrong, the buyer is protected.
Other Triggers for Earn-Out Structures
Beyond the valuation gap, earn-outs appear in several other Japan M&A situations:
(a) Regulatory uncertainty: where a product approval, a license renewal, or a government contract is pending at closing, and the business value depends materially on the outcome.
(b) Key-person retention: where the seller is also the business's primary revenue generator and the buyer needs to incentivize continued performance post-closing without paying full value upfront.
(c) Financing constraints: where the buyer cannot fund the full consideration at closing and structures deferred payments around projected cash flows from the acquired business.
(d) Succession-driven deals: many Japanese business succession transactions involve sellers who are not purely financially motivated and who want some form of ongoing validation that the business thrives under new ownership. An earn-out can serve that function even where the pure economics would not require one.
How Earn-Outs Work in a Japan M&A Context
Basic Structure
An earn-out divides the total consideration into two components: a fixed amount payable at closing, and a contingent amount payable in one or more future tranches subject to the business meeting agreed performance milestones. The share purchase agreement (株式譲渡契約, SPA) will define:
(a) the earn-out period: typically one to three years from closing, though longer periods are seen in deals with regulatory milestones;
(b) the performance metric or metrics to be measured;
(c) the measurement methodology and accounting standard to be applied;
(d) the calculation procedure, including who prepares the earn-out statement, the timeline, and the dispute resolution process;
(e) the cap on earn-out consideration and any threshold below which no earn-out is payable;
(f) the buyer's obligations during the earn-out period with respect to operating the business.
Japanese Structural Nuances
Japanese SPAs are often shorter and less prescriptive than Anglo-American equivalents, reflecting the civil law tradition under Civil Code (民法) where good faith obligations fill contractual gaps. This creates risk in earn-out drafting: parties sometimes rely on implied obligations where an Anglo-American practitioner would spell out every scenario in express language. In earn-out provisions, reliance on implied terms is dangerous. The earn-out calculation, the buyer's operational obligations, and the dispute resolution mechanism should all be set out exhaustively, not left to the principle of good faith and fair dealing (信義誠実の原則) to resolve.
Japanese M&A deals, even cross-border ones, are often governed by Japanese law. Foreign buyers sometimes attempt to import English or New York law SPA structures wholesale. That approach creates ambiguity when Japanese courts or arbitral tribunals are asked to interpret provisions drafted in a foreign legal tradition without adaptation to the Japanese legal framework.
Earn-Out vs Completion Accounts vs Locked-Box: The Three Price Adjustment Mechanisms
These three mechanisms address the same underlying problem, which is uncertainty about the financial state and future performance of the business at and after the point of closing, but they address it in different ways and at different points in the deal timeline.
Earn-Out
An earn-out is forward-looking. It pays additional consideration if the business achieves future milestones. It is appropriate when the valuation disagreement is primarily about future performance rather than the current financial position of the business. The earn-out period continues post-closing, meaning the buyer is operating the business while the earn-out accrues. This creates the central tension of any earn-out: the buyer controls the business and therefore controls the inputs that determine whether the earn-out is paid.
Completion Accounts
A completion accounts mechanism is backward-looking and price-adjusting. The SPA fixes a base price, but the final consideration is adjusted upward or downward based on a closing balance sheet prepared as of the actual closing date. The typical completion accounts formula adjusts for: (a) the actual level of net working capital compared to a target; (b) actual cash and debt at closing; and (c) sometimes actual normalized earnings. The completion accounts mechanism is appropriate when there is uncertainty about the financial position of the business at closing but not about its future performance.
Locked-Box
A locked-box mechanism is also backward-looking but uses a fixed reference date balance sheet rather than a closing balance sheet. The economic risk and reward of the business transfers to the buyer on the locked-box date, not on the closing date. The seller receives the consideration agreed at signing without further adjustment, provided no unauthorized value has leaked out of the business between the locked-box date and closing.
Practical Comparison
These three mechanisms are not mutually exclusive. A deal might use a locked-box for the base price and an earn-out for the contingent element. A deal might use completion accounts to determine closing consideration and an earn-out for post-closing performance. The choice depends on which party bears more risk, what the source of uncertainty is, and what each party is willing to accept in negotiations.
Designing Earn-Out Milestones
The choice of milestone is the most consequential drafting decision in any earn-out. A poorly designed milestone creates disputes even when the business performs well.
Revenue-Based Milestones
Revenue milestones are common because revenue is relatively easy to measure and difficult for a buyer to manipulate by changing accounting policies. The principal risk is that the buyer can depress earn-out revenue by reallocating customers to a different entity, refusing to invest in growth, or pricing contracts below market to benefit a related buyer entity at the expense of the target.
Protective drafting: define revenue to include all amounts that would have been recognized by the target if it had continued to operate independently, and include anti-manipulation provisions that require revenue to be recognized in a manner consistent with the methodology applied in the prior two years.
EBITDA-Based Milestones
EBITDA milestones reward profitability rather than just top-line growth, which better aligns with buyer incentives post-closing. However, EBITDA is significantly more susceptible to manipulation. A buyer can increase the target company's costs by: charging management fees or intercompany service fees; reallocating shared costs from the group to the target; underfunding the target's marketing, headcount, or capital expenditure; or accelerating depreciation. Each of these actions reduces EBITDA and reduces the earn-out payment.
Protective drafting: define EBITDA to exclude any intercompany charges not present before closing (or cap them at a market rate), require the business to be funded at a level consistent with its pre-closing budget, and prohibit the buyer from using the target as a cost center for group expenses during the earn-out period.
Operational Milestones
Operational milestones tie earn-out payments to specific events: obtaining a regulatory approval, renewing a key customer contract, completing a product launch, or achieving a technical certification. These are appropriate when the business value genuinely depends on a binary event rather than a financial trajectory.
The primary risk is that the buyer controls or influences whether the event occurs. A buyer who no longer wants to pay the earn-out can delay a regulatory application or deprioritize the product launch.
Protective drafting: require the buyer to use commercially reasonable efforts to achieve the milestone, and define a deemed-achieved provision if the buyer fails to take required actions within a specified timeframe.
Comparative Assessment
(a) Revenue milestones: simpler, harder to manipulate on the cost side, but can be gamed through customer reallocation and pricing.
(b) EBITDA milestones: better aligned with deal value but expose sellers to cost-loading risk; require detailed anti-manipulation provisions.
(c) Operational milestones: appropriate for binary events; require best-efforts obligations and deemed-achievement carve-outs.
(d) Hybrid milestones: combining a revenue floor with an EBITDA ratio, or pairing a financial metric with an operational condition, can balance the risks.
The Enforcement Challenge: Earn-Out Disputes Under Japanese Law
Contract Enforcement Framework
Earn-out obligations are contractual obligations governed by Civil Code (民法). Under 民法第415条, non-performance of a contractual obligation gives rise to a damages claim where the non-performance is attributable to the obligor. The 2020 Civil Code reform replaced the prior fault-based test with an attributability test, which is slightly more favorable to claimants in straightforward breach situations.
However, earn-out disputes are rarely clean breach cases. The typical dispute involves a disagreement about whether the buyer's conduct of the business constitutes a breach of an obligation to operate the business in a manner that gives the earn-out a fair opportunity to be achieved. Courts assessing this question will look to the express contractual language and, where it is ambiguous, to the principle of good faith (信義誠実の原則). The outcome is uncertain unless the buyer's obligations are drafted with specificity.
Arbitration vs Litigation
Most cross-border Japan M&A transactions include an arbitration clause rather than a submission to the courts. The Arbitration Act (仲裁法) governs domestic arbitration in Japan and implements the UNCITRAL Model Law. Institutional rules commonly used in Japan M&A earn-out disputes include the Japan Commercial Arbitration Association (日本商事仲裁協会, JCAA) Commercial Arbitration Rules and the ICC Rules of Arbitration. The JCAA Fast Track procedure applies to disputes below JPY 50 million and can resolve claims in compressed timeframes.
Practical note: arbitration is generally preferable to litigation for earn-out claims for three reasons. First, arbitral proceedings are confidential, which matters when a buyer does not want a pricing dispute publicized. Second, arbitrators with M&A experience can be appointed, whereas court judges in Japan may have limited familiarity with earn-out mechanics. Third, New York Convention enforcement enables cross-border enforcement of an award if one party has assets in multiple jurisdictions.
The SPA should specify: the arbitral institution, seat of arbitration, language, and number of arbitrators. It should also include an accounting expert determination procedure specifically for earn-out calculation disputes, which are typically faster and cheaper to resolve than full arbitration when the dispute is purely about numbers rather than conduct.
Buyer Behavior Risk: Protecting Sellers During the Earn-Out Period
The earn-out period is the interval during which a seller is most exposed to buyer conduct risk. The buyer controls the target company after closing and can take actions that reduce measured performance without violating any express term of the SPA, unless the SPA was drafted to anticipate those actions.
Common Buyer Actions That Undermine Earn-Outs
(a) Cutting marketing or sales expenditure: reducing the budget allocated to the target's commercial activities, either absolutely or relative to the pre-closing run rate, directly impacts revenue without any nominal breach of contract.
(b) Reallocating customers or revenue: directing new business opportunities or customer relationships to a different group entity rather than the target, or migrating existing customers to a group-level contract that bypasses the target.
(c) Intercompany cost loading: imposing management fees, IT service charges, or shared services charges on the target at rates above market, inflating the target's cost base and suppressing EBITDA.
(d) Refusing to resource the business: failing to approve headcount replacements, capex, or growth investments that the seller would have made when operating independently.
(e) Integration actions: merging the target's operations, systems, or teams into the broader group in a way that makes attribution of earn-out performance practically impossible.
Contractual Protections Sellers Should Demand
Express operational obligations: the SPA should require the buyer to operate the target in the ordinary course of business consistent with past practice during the earn-out period, to maintain the target's headcount and budget at levels consistent with the pre-closing plan, and to refrain from taking any action for the primary purpose of reducing earn-out consideration.
Prohibition on intercompany charges: the SPA should either prohibit new intercompany charges during the earn-out period or cap them at rates demonstrably consistent with market pricing.
Non-diversion covenant: the SPA should include a covenant that any business opportunity that would, in the ordinary course, have been directed to the target must continue to be directed to the target during the earn-out period.
Deemed-achievement clause: if the buyer integrates the target in a way that makes earn-out measurement impossible, the earn-out should be deemed achieved at the target amount.
Earn-out committee or information rights: sellers should negotiate ongoing access to management accounts during the earn-out period, participation in budget discussions affecting the target, and in some cases a seat on an earn-out oversight committee.
GAAP vs J-GAAP: Accounting Differences and Earn-Out Measurement
Why Accounting Standards Matter
An earn-out measured in EBITDA or revenue can produce materially different results depending on whether it is calculated under Japanese Generally Accepted Accounting Principles (日本基準, J-GAAP), International Financial Reporting Standards (IFRS), or US GAAP. A target that has historically prepared financial statements under J-GAAP will produce different metrics under IFRS revenue recognition standards (IFRS 15), different lease obligations (IFRS 16 vs J-GAAP operating lease treatment), and different treatment of various accruals. If the SPA does not specify which accounting standard governs the earn-out calculation, disputes will arise.
Key J-GAAP Differences Affecting Earn-Out Calculations
Revenue recognition: J-GAAP historically permitted more flexible revenue recognition than IFRS 15, though Japan began aligning with IFRS 15 principles under Accounting Standard for Revenue Recognition (企業会計基準第29号). For earn-out purposes, the question is whether the target's historical J-GAAP accounting policies, or a revised IFRS-aligned standard, are applied consistently throughout the earn-out period.
Lease accounting: IFRS 16 requires most leases to be capitalized on the balance sheet, adding back depreciation and interest in an EBITDA calculation while also reducing operating cash outflows. J-GAAP operating lease treatment keeps these payments off-balance-sheet and as operating expenses. A target with significant operating lease commitments will show materially different EBITDA under each standard.
Goodwill amortization: J-GAAP requires goodwill to be amortized (typically over 20 years or less), while IFRS uses an impairment-only model. If the earn-out calculation excludes amortization of acquisition-related goodwill but the definition is not explicit, J-GAAP amortization charges could distort the earn-out EBITDA.
Provision and accrual practices: J-GAAP and IFRS differ in their approach to provisions, particularly retirement benefit obligations (退職給付引当金) and warranty provisions. A buyer shifting the target to group accounting standards mid-earn-out can create artificial variation in reported earnings.
Drafting the Accounting Standard Clause
The earn-out calculation clause must: (a) specify which accounting standard applies; (b) require that standard to be applied consistently with the methodology used in the target's most recent audited financial statements prior to closing; and (c) prohibit changes in accounting policy during the earn-out period that would have the effect of reducing earn-out payments, unless required by law or applicable accounting standards, in which case the parties agree to negotiate a good-faith adjustment.
Tax Treatment of Earn-Out Payments
Japanese Tax Framework for Earn-Outs
Earn-out payments received by a seller are additional consideration for the transfer of shares. Under Corporate Tax Act (法人税法), a corporate seller recognizes gain on share disposal when the right to receive consideration becomes fixed and ascertainable. For earn-out payments, there are two possible positions:
(a) Recognition at closing: if the full earn-out entitlement can be reasonably estimated at closing, the NTA may take the position that the full consideration, including the estimated earn-out, is taxable in the year of closing.
(b) Recognition when determined: if the earn-out is genuinely contingent and cannot be estimated at closing, gain on each earn-out tranche is recognized when the amount is determined and payable. This is the more common practical outcome for earn-outs with genuine performance uncertainty.
Individual sellers who are Japan residents recognize earn-out receipts as capital gains (譲渡所得) at the time each payment becomes fixed.
Recommendation: obtain NTA guidance or tax opinion before closing on the timing of recognition, particularly in large deals where recognition timing creates material cash flow differences.
Withholding Tax on Cross-Border Earn-Out Payments
Where the seller is a non-resident of Japan, earn-out payments made by a Japan-resident buyer may be subject to Japanese withholding tax. The applicable withholding rate under domestic law is 20.42% on the gross payment for certain categories of income. Applicable bilateral tax treaties typically reduce this rate for capital gains, and many treaties exempt capital gains on share disposals entirely, depending on the structure.
Critical points for cross-border deals:
(a) Identify the treaty position for each earn-out payment before the SPA is executed; the tax analysis may differ from the analysis at closing if earn-out payments occur in a different tax year.
(b) Confirm whether each earn-out tranche is characterized as capital gains or income from property under the applicable treaty, as the withholding treatment differs.
(c) File the applicable reduced-rate certificate with the Japan payer before the payment is made; failure to file results in the withholding being applied at the domestic rate.
(d) The seller should account for the possibility of withholding in the net consideration model, particularly if there is no gross-up obligation in the SPA.
The Locked-Box Mechanism in Japan
How It Works
A locked-box transaction uses a historical balance sheet, prepared as of a reference date (the "locked-box date"), as the agreed financial basis for the purchase price. The purchase price is fixed at signing based on that balance sheet, and it does not change between signing and closing. The economic benefit and risk of the business pass to the buyer as of the locked-box date.
In exchange for this price certainty, the seller undertakes not to allow any unauthorized value to flow out of the business ("leakage") between the locked-box date and closing.
Leakage and Permitted Leakage
Leakage typically includes: (a) dividends or distributions to the seller or seller-connected parties; (b) payments of management fees or other charges to related parties not made on arm's-length terms; (c) asset transfers to related parties below market value; (d) waiver of amounts owed to the target by related parties; (e) transaction bonuses or compensation increases to related parties outside the ordinary course of employment.
Permitted leakage is the category of value transfers that the parties have pre-agreed will not constitute a breach: ordinary course salary payments to employed sellers, pre-agreed transaction bonuses disclosed in the SPA, and certain tax payments that are disclosed and agreed.
Advantages for Sellers
The locked-box mechanism is generally seller-preferred: the price is fixed and cannot be adjusted downward after signing, there is no post-closing dispute risk about closing balance sheet calculations, and the seller can plan around a known receipt. It is less suitable when the business is volatile, when there is material uncertainty about working capital, or when the buyer has not completed deep financial due diligence before signing.
The Completion Accounts Mechanism
Closing Balance Sheet and Adjustment Formula
A completion accounts mechanism requires the preparation of a closing balance sheet as of the actual closing date, which is used to calculate the final purchase price through an adjustment formula. The typical formula adjusts the base equity value for:
(a) the difference between actual net working capital at closing and an agreed target net working capital figure;
(b) actual cash and cash equivalents at closing (added to price);
(c) actual financial debt at closing (deducted from price);
(d) sometimes, additional items such as normalized earnings, unfunded pension liabilities, or specific contingent liabilities.
Dispute Resolution for Completion Accounts
Completion accounts disputes are among the most common post-closing disputes in M&A transactions globally. In Japan deals, these disputes typically arise from: (a) disagreements about whether specific items should be included in working capital; (b) application of accounting policies differently from historical practice; and (c) timing differences in recognizing accruals or provisions.
The SPA should require: (a) accounting policies consistent with those applied in the target's most recent audited accounts; (b) a structured challenge process with a specified timeline; and (c) referral to an independent accounting expert for unresolved disputes.
When to Use Each Mechanism: Practical Decision Framework
Use a Locked-Box When:
(a) the deal is seller-driven and the seller has negotiating leverage to insist on price certainty;
(b) the target has clean, audited financials and the locked-box date accounts have been prepared with appropriate care;
(c) the period between signing and closing is predictable and short;
(d) working capital fluctuations are modest and well understood from due diligence.
Use Completion Accounts When:
(a) the buyer lacks confidence in the locked-box date balance sheet and wants to pay for what it actually receives at closing;
(b) the business has volatile working capital (seasonal inventory, construction contracts, project billing);
(c) the time between signing and closing is long and material changes to the financial position are expected.
Use an Earn-Out When:
(a) the valuation gap between buyer and seller cannot be resolved through price negotiation alone;
(b) the business's value depends materially on future performance that the seller believes in but the buyer cannot verify from historical data;
(c) the seller is remaining with the business post-closing and the earn-out serves a retention and performance-alignment function;
(d) a specific regulatory, contractual, or operational milestone is genuinely material to value and is pending at closing.
The Hybrid Approach
Many Japan M&A deals above a certain size use a hybrid: a locked-box or completion accounts mechanism for the closing price combined with an earn-out for the contingent element. The base mechanism provides price certainty on the current value of the business; the earn-out provides upside for the seller if the investment thesis is validated. In the hybrid structure, the anti-manipulation protections for the earn-out are as important as in a pure earn-out deal, because the same buyer conduct risks apply regardless of how the base price was determined.
Conclusion
Earn-out structures, completion accounts, and locked-box mechanisms are complementary tools for allocating pricing risk in Japan M&A transactions. The earn-out is the most complex and litigation-prone of the three, and it requires precise drafting of milestones, accounting standards, buyer operational obligations, and dispute resolution procedures to be effective. The locked-box offers sellers price certainty but requires robust leakage protection and reliable pre-signing financials. Completion accounts offer buyers flexibility but create post-closing dispute risk that must be managed through disciplined process and clear drafting.
Governing law, accounting standards, and enforcement forum must be addressed at the term sheet stage. In Japan cross-border deals, the interaction between Civil Code (民法), Companies Act (会社法), J-GAAP, and applicable tax treaties creates a specific framework that differs materially from Anglo-American M&A practice. Foreign buyers and sellers who import contract structures without adapting them to the Japan legal context will encounter difficulties that careful upfront drafting would have avoided.
This article is for informational purposes only and does not constitute legal or financial advice. Consult qualified Japanese legal and financial advisors for your specific transaction.