An offshore fund ("SLT"), in which the taxpayer had an interest, invested in instruments (labelled as "Notes") of non-resident subsidiaries of Canadian banks that had been issued for US $998 million and guaranteed by those banks. They did not bear interest and provided for a payment on maturity (15 years after their issuance, subject to earlier repayment after having given 367 days’ notice) that reflected the performance of a matching actively-managed portfolio of assets (the “Reference Assets”) held by affiliates of the obligors. If the Notes constituted "debts" for purposes of s.