Goodwill

The excess of what an acquirer paid over the fair value of the identifiable net assets it bought. It is not an asset in any ordinary sense; it is the accounting record of a price.

A company pays ₹1,800 crore for a business whose identifiable net assets are fairly valued at ₹1,150 crore. The ₹650 crore difference is recorded as goodwill and stays on the balance sheet indefinitely.

Goodwill isn't amortised under Ind AS, IFRS or US GAAP for public companies; the older Indian GAAP, still used by smaller unlisted companies, amortises goodwill arising on an amalgamation, and US private companies may elect to amortise it. It's tested for impairment at least annually, and written down when the acquired business no longer supports the price paid. Those write-downs tend to arrive years late and all at once.

Understanding the impairment test itself explains the delay. Goodwill is tested at the level of the cash-generating unit it was allocated to, and the recoverable amount is the higher of fair value less costs to sell and value in use, where value in use is a discounted cash flow built on management's own forecasts. Management chooses the forecast and the growth rate. It also picks the discount rate, and the note discloses all of them. An impairment therefore comes when those assumptions become impossible to defend. The point when the acquired business first started to disappoint comes earlier and passes without a charge.

For analysis, subtract goodwill before computing return on capital if you want to know what the operating business earns, and leave it in if you want to know what the shareholders' money earned. Both questions are legitimate. Say which you asked.