Goodwill

Goodwill is the premium an acquirer pays above the fair value of a target's identifiable net assets, parked on the balance sheet as an intangible asset. Buy a company for $500M whose nameable assets minus liabilities are worth $320M, and $180M of goodwill appears — the accounting residue of whatever justified the price: brand, synergies, or optimism.

Goodwill is never amortized; instead it is tested for impairment at least annually. When the acquired business underperforms, the company writes goodwill down, taking a non-cash charge that amounts to a public admission of having overpaid. Large impairments often arrive years after the deal, long after the executives who struck it have moved on.

For valuation, goodwill inflates book value with an asset that cannot be sold or redeployed, which is why conservative measures like tangible book value strip it out entirely.