Impairment and Derecognition

Under IFRS, when does a long-lived asset fail the one-step impairment test?

When carrying amount exceeds recoverable amount.

A machine has a carrying amount of $100$, fair value less costs to sell of $92$, and value in use of $95$. Under IFRS, is it impaired and by how much?

Yes; impairment loss is $5$.

How do you calculate gain or loss on disposal of a long-lived asset?

Proceeds minus carrying amount (net book value).

In IFRS impairment testing, why is recoverable amount defined as the higher of fair value less costs to sell and value in use?

Because recoverable amount reflects the best amount recoverable from sale or use.