Finite vs. indefinite life
Finite-lived intangibles (e.g., patents, customer lists with a determinable life) are amortized over their useful life and tested for impairment only when indicators exist (same recoverability-then-fair-value model as PP&E). Indefinite-lived intangibles (e.g., some trademarks, goodwill) are not amortized but tested for impairment at least annually.
Research & development
IMPORTANT: Under US GAAP, R&D costs are generally expensed as incurred — this is a major difference from IFRS, which capitalizes qualifying development costs once technical feasibility is established. Purchased in-process R&D acquired in a business combination is capitalized; internally generated R&D is not.
Software development costs follow their own rules: costs incurred before technological feasibility is established are R&D (expensed); costs after technological feasibility but before general release are capitalized and amortized.
Goodwill
Goodwill arises only in a business combination — it can never be internally generated and capitalized. It's tested for impairment at least annually at the reporting unit level (a simplified one-step test: if a reporting unit's carrying value, including goodwill, exceeds its fair value, an impairment loss is recognized for the difference, capped at the amount of goodwill allocated to that unit).
EXAMPLE: A reporting unit has a carrying value of $12M (including $3M of goodwill) and a fair value of $10.5M. Impairment = $12M − $10.5M = $1.5M, which is less than the $3M of goodwill, so the full $1.5M reduces goodwill (goodwill can't go below zero).
EXAM TIP: Private companies can elect an accounting alternative to amortize goodwill straight-line over 10 years (or less) and test for impairment only upon a triggering event — know that this alternative exists but is private-company-specific.