Which model is only available under IAS 38 if there is an active market for the intangible?

The correct choice pertains to the revaluation model under IAS 38, which applies specifically when there is an active market for the intangible asset. This model allows for the fair value of an intangible asset to be remeasured regularly to reflect current market conditions. If there is an active market, reliable fair value measurements are possible, making this model appropriate for revaluing intangible assets.

Using the revaluation model means that any increases in asset value are recognized in other comprehensive income, typically creating a revaluation surplus in equity. This provides a more accurate representation of the asset's value reflecting its current market conditions, which is particularly relevant for investors and stakeholders seeking an understanding of a company's true financial position.

Other models, such as the cost model, do not allow for revaluation and instead require intangible assets to be carried at cost minus accumulated amortization and any impairment losses. Therefore, they do not provide the same level of insight into changes in value as the revaluation model does. This distinction underlies why the revaluation model is uniquely tied to the existence of an active market for the intangible asset.