Completion accounts are financial statements drawn up after completion to work out whether the price needs adjusting, based on the actual working capital, net debt, or net assets the business had on the day it changed hands.
Technically, they are post-completion accounts prepared under an agreed methodology in the sale agreement, comparing actual completion-date figures against pre-agreed targets, with any shortfall or surplus adjusting the price paid.
The buyer wants completion accounts because they let the price be trued up to what the business actually looked like on the day, protecting against a seller who quietly ran down cash or stock before handover. The seller often prefers the certainty of a locked-box mechanism instead, because completion accounts mean the final price is not really known until months after the money changes hands.
Where completion accounts are used, the accounting methodology decides the outcome far more than the headline price does. Whoever controls the definitions, accounting policies, and treatment of disputed items effectively controls the adjustment.
What you as a seller should push back on: a methodology that lets the buyer choose accounting treatments after the fact rather than fixing them in the agreement upfront, and a dispute mechanism that leaves the buyer’s own accountants as the effective final word.