If you disposed of a T-bill at maturity in 2012, you have to report as interest the difference between the price you paid and the proceeds of disposition shown on your T5008 slip or account statement.
If you disposed of a T-bill before maturity in 2012, you may also have to report a capital gain or loss. For more information, see "T-bills" in Guide T4037, Capital Gains.
Enter on line 121 the total interest and investment income.