Definition of 'Write-Up'
An increase made to the book value of an asset, because its carrying value is less than fair market value. A write-up generally occurs if a company is being acquired and its assets and liabilities are restated to fair market value, under the purchase method of M&A accounting. It may also occur if the initial value of the asset was not recorded properly, or if an earlier write-down in its value was too large. An asset write-up is the opposite of a write-down and both are non-cash items.
Investopedia explains 'Write-Up'
For example, assume Company A is acquiring Company B for $100 million, at which point the book value of Company B's net assets was $60 million. Before the acquisition can be completed, Company B's assets and liabilities have to be marked-to-market to determine their fair market value (FMV).
If the FMV of Company B's assets is determined to be $85 million, the increase in their book value of $25 million represents a write-up. The difference of $15 million between the FMV of Company B's assets and the purchase price of $100 million, is booked as goodwill on Company A's balance sheet.