The defaulted amount, for both Recoverable and Non-Recoverable Default, cannot be used to offset your income tax payment. This is because the defaulted Note is not a write-off case since the recovery effort is a continuous progress. The Non-Recoverable classification does not mean that all efforts to recover the defaulted amount has been ceased, but it is to help investors to have a better view on their portfolio.
We have referred to this matter with Lembaga Hasil Dalam Negeri (LHDN), however you may reach out to LHDN directly to obtain further clarity.