They're two ways of fixing the final price in a share purchase. A locked box sets the price from a past balance sheet. Completion accounts adjust the price after completion, based on the company's actual position on the day.
Locked box
- The price is fixed from a balance sheet at an agreed date before completion.
- The seller promises no value leaks out between that date and completion, such as dividends or unusual payments to themselves.
- You carry the trading risk in between, good or bad.
- Simpler and more certain: you know the price at signing.
Completion accounts
- The price is adjusted after completion for the company's actual cash, debt and working capital on the day.
- The seller carries the trading risk until completion.
- Takes longer, and the adjustment can lead to disagreements.
Why it matters for your funding
The final price affects how much you need to borrow and when. A post-completion adjustment can mean paying extra, or getting money back, after the deal.
Get advice
Your solicitor and accountant will recommend which suits your deal.
Last reviewed: 8 October 2026