Perpetual debt instruments

[From Guidance on implementing IFRS 9 Financial Instruments]

Definition of gross carrying amount: perpetual debt instruments with decreasing interest rate

If the stated rate of interest on a perpetual debt instrument decreases over time, would the gross carrying amount equal the contractual par amount in each period?

No. From an economic perspective, some or all of the contractual interest payments are repayments of the gross carrying amount. For example, the interest rate may be stated as 16 per cent for the first 10 years and as zero per cent in subsequent periods. In that case, the initial amount is amortised to zero over the first 10 years using the effective interest method, since a portion of the contractual interest payments represents repayments of the gross carrying amount. The gross carrying amount is zero after Year 10 because the present value of the stream of future cash payments in subsequent periods is zero (there are no further contractual cash payments in subsequent periods).