What happens if the working capital number the seller gave me at closing turns out to be wrong?

A wrong working-capital number is usually handled first through the purchase agreement's own adjustment mechanism rather than as an ordinary indemnity claim. Most agreements provide for an estimated closing statement followed by a final statement, with a defined process — commonly referral to an independent accountant — for resolving disagreements about the calculation itself. If your dispute is really about how the number was calculated under the agreed accounting methodology, that mechanism is generally where it belongs.

If instead the underlying figures were misrepresented or manipulated rather than simply calculated in good faith under a disputed methodology, that shifts the analysis toward an indemnity or misrepresentation claim for the underlying inaccuracy, rather than an ordinary adjustment disagreement. Which category your situation actually falls into changes both the process you follow and what you can ultimately recover, so identifying that distinction early — is this a calculation dispute or a false-information problem — matters more than jumping straight to either process.