Treasury Bills are always something it's necessary to look up when it comes to accounting for tax.  Is it interest or is it capital?

If it's disposed of AT MATURITY, any difference between what you paid and what you received as proceeds is interest income.

It's when you dispose of it before matuirty, that you may also have a gain or loss on account of capital.
and they don't make it easy to find... but here in T4037 is where you find how to calculate how much is interest and how much is capital:
http://www.cra-arc.gc.ca/E/pub/tg/t4037/t4037-e.html#P821_67887

First you have to know your purchase price and the effective yield rate and how many days you held it and the number of days in the year you sold to calculate how much is interest income. 

Then the difference between how much you sold it for less interest less what you paid for it is a capital gain or loss.