TLDR: Locked box and completion accounts answer the same question in opposite ways: when does economic ownership of a target company pass from seller to buyer? A locked box fixes the equity price at a historic accounts date and protects the buyer only through anti-leakage covenants; completion accounts leave the price open until a post-closing true-up based on actual net debt and working capital. Locked box structures now feature in 62% of European private M&A deals, while in the United States a post-closing adjustment still appears in roughly nine out of ten private-target deals. Neither approach is universally right. The correct choice depends on how reliable the target’s numbers are, how long the gap between signing and closing will be, and how much post-closing friction the parties are prepared to absorb.
The Question Beneath the Price Tag
Every share purchase agreement has to answer a deceptively simple question: at what moment does the buyer start owning the economics of the business it is acquiring? Get this wrong in drafting and the parties spend the months after signing arguing over receivables provisions and inventory reserves instead of running the business. Get it right and the mechanism becomes almost invisible, a piece of financial plumbing that nobody thinks about again once the deal has closed.
Completion accounts answer the question literally: ownership, in an economic sense, transfers at completion. The buyer pays a provisional price on closing day based on estimated net debt, cash and working capital, and its accountants then prepare a final set of accounts, usually within 60 to 90 days, reflecting the target’s actual position at the moment of transfer. The purchase price moves up or down to match.
A locked box answers the same question by moving the clock backward. The parties agree the price up front, calculated from the target’s most recent audited or reviewed accounts as of a specified “locked box date,” and there is no adjustment after closing regardless of what completion accounts might later show. Economically, the buyer takes on the risk and benefit of the business from that locked box date, not from the date the deal actually closes.
How the Locked Box Actually Works
The mechanics matter because the locked box shifts risk onto the buyer well before it takes legal control. Once the locked box date is set, usually the target’s last financial year end so that audited numbers can anchor the price, the seller commits not to extract value from the business before completion. Dividends, intercompany charges, transaction bonuses and off-market related-party payments are all captured under a defined term of art: leakage. Any leakage that is not specifically carved out as “permitted leakage” is repayable to the buyer, typically pound for pound and on an uncapped basis, within a relatively short claim window after completion.
Because the price is agreed on historic accounts, sellers in a profitable business will usually ask for something in return for the value that accrues between the locked box date and completion. This is the equity ticker, a daily interest-like charge on the fixed equity value, sometimes calculated as a straight interest rate and sometimes tied to the cash the business is expected to generate over that period. It compensates the seller for handing over the economics of a growing business before it actually receives payment for it.
The appeal of this structure to sellers is straightforward: a locked box produces a single, comparable number in a competitive auction, removes the scope for a buyer to renegotiate price through aggressive post-closing accounting, and lets a private equity seller return proceeds to its investors without waiting on a completion accounts process to resolve. It is no accident that locked box mechanisms are most entrenched in auction sales where the seller is a financial sponsor.
How Completion Accounts Actually Work
Completion accounts pursue precision rather than certainty. The theory is appealing: rather than betting on a historic snapshot, the buyer pays for exactly what it receives, measured at the point it receives it. In practice, that precision is harder to achieve than the mechanism implies, because the line items that move the price most, receivables provisions, inventory obsolescence reserves and accrual completeness, all depend on accounting judgment rather than objective fact.
The structural problem is timing. By the time the completion accounts are prepared, the buyer already controls the target’s finance function and has every incentive to take a conservative view of working capital, since a lower number means a lower final price. The seller, meanwhile, is arguing about numbers it no longer controls. This is why completion accounts disputes concentrate so heavily on the same handful of line items across unrelated deals, and why an escrow or holdback is standard practice to fund whatever adjustment eventually gets agreed.
Completion accounts remain the default answer in the United States for good reason: they let a buyer walk away from an unfamiliar target without pricing every contingency into the headline number at signing. Working capital purchase price adjustments now appear in more than 90% of private-target US transactions, up from roughly 50% a decade ago, and a separate study of 139 US acquisition agreements found a post-closing purchase price adjustment mechanism in 90% of deals executed in 2024 and early 2025.
Locked Box vs Completion Accounts at a Glance
| Dimension | Locked Box | Completion Accounts |
|---|---|---|
| When price is fixed | At signing, by reference to a historic accounts date | After completion, by reference to actual figures |
| Who bears interim risk | Buyer, from the locked box date | Seller, until completion |
| Buyer’s key protection | Anti-leakage covenant and warranties | Post-closing price adjustment |
| Where uncertainty is resolved | Before signing, through diligence | After closing, through accounting process |
| Typical dispute point | Characterisation of leakage | Receivables, inventory and accrual judgment calls |
| Generally favours | Seller | Buyer |
Why Europe Chose the Locked Box, and the US Mostly Hasn’t
The divergence between the two markets is not accidental. CMS’s annual European M&A Study recorded locked box arrangements in 62% of the 509 deals it tracked in 2022, up from 51% in 2020, and the figure rose to 79% for deals valued up to EUR 100 million. Private equity’s dominance of European auction processes explains much of this. When several bidders are competing for the same asset on a tight timetable, a seller wants offers it can compare on a like-for-like basis, and a locked box delivers exactly that: one number, fixed at signing, unaffected by how aggressively a given bidder later chooses to interpret working capital.
The US market has evolved differently, in part because purchase price adjustment mechanisms became deeply embedded in deal practice well before locked box structures gained traction, and in part because buyers accustomed to that protection have been reluctant to give it up. The result is two mature but distinct market conventions rather than one approach that is objectively superior. A Swiss or European seller negotiating with a US strategic buyer, or a European fund selling into an American trade acquirer, should expect this divergence to surface early in term sheet discussions.
Choosing the Right Mechanism for Your Deal
The decision comes down to three practical questions. First, how reliable are the target’s numbers? A locked box depends on accounts that can bear real diligence weight, whether audited financial statements or a well-supported set of management accounts; where the underlying data is thin, a completion accounts process gives the buyer a second look after closing that diligence alone cannot replicate. Second, how long is the gap between signing and completion? The longer that period, the more exposed a buyer becomes to a locked box’s staleness, and the more an equity ticker or interim reporting obligations need to be negotiated to compensate. Third, how much appetite do the parties have for post-closing process? Sellers under pressure to distribute proceeds quickly, and buyers who want management focused on the business rather than a completion accounts exercise, both tend to gravitate toward the locked box; buyers acquiring a carve-out or a business with volatile working capital often insist on the discipline of a true-up.
This is where an advisor earns its fee. The pricing mechanism interacts with almost every other term in the SPA: warranty scope, escrow structure, the leakage schedule, indemnity caps, and getting the interaction wrong costs more in dispute costs and delayed proceeds than it ever saves in negotiating leverage. Neumarz advises Swiss and European mid-market companies and their shareholders through exactly this kind of structuring decision, weighing the quality of a target’s financial reporting, the realistic timetable to completion and each party’s tolerance for post-closing friction before recommending a mechanism, rather than defaulting to whichever one a template happens to favour. Choosing between a locked box and completion accounts is not a clause to be filled in late in drafting; it is a decision that should be made deliberately, with the rest of the deal built around it.
References
- CMS. “CMS European M&A Study 2023: Record number of deals last year despite challenging economic backdrop.” https://cms.law/en/int/legal-updates/cms-european-m-a-study-2023-record-number-of-deals-last-year-despite-challenging-economic-backdrop
- DLA Piper. “Locked box: Price protection, not price adjustment.” https://www.dlapiper.com/en/insights/publications/2017/07/locked-box
- SRS Acquiom. “2025 Working Capital Purchase Price Adjustment Study.” https://www.srsacquiom.com/our-insights/2025-working-capital-purchase-price-adjustment-study/
- Wagner Hicks PLLC. “The New Normal in Private M&A: Key Takeaways from the 2025 ABA Deal Points Study.” https://www.wagnerhicks.law/the-new-normal-in-private-ma-key-takeaways-from-the-2025-aba-deal-points-study/
