Which method is used to subsequently measure perpetual debt?

The correct approach to subsequently measure perpetual debt is through amortized costs using the effective interest method. This method involves calculating interest expense based on the carrying amount of the debt and the effective interest rate at the time of issuance.

Perpetual debt, which has no fixed maturity date, is typically issued with a fixed interest rate, and the effective interest method allows for the recognition of interest expense over time in a way that reflects the actual cost of borrowing. Under this method, accrued interest is added to the carrying value of the debt, and the interest expense recognized will include both the cash interest paid and the amortization of any premium or discount on the issuance of the debt.

Using current market value or fair value based on current interest rates would not be appropriate for measuring perpetual debt in subsequent periods. This is because these methods reflect changes in market conditions that may not align with the contractual cash flows of the debt itself. Moreover, acquisition cost simply reflects the amount paid at the date of purchase, which does not take into account the amortization process or ongoing interest expense recognition.

In summary, the effective interest method aligns with how interest is accrued and recognized over time, making it the correct choice for measuring perpetual debt after it has been initially recorded.