Well, in this case the upshot of this measure deals not so much with corporations that don't pay tax to the CRA. They will pay interest on their underpaid taxes at the treasury bill rate plus 4%, as would any individual. This measure deals with overpayments of tax, effectively leaving moneys on deposit with the Canada Revenue Agency. Part of this policy recognizes that the Canada Revenue Agency is not a deposit-taking institution; it is an institution that collects tax. Interest is paid on tax overpayments, and that's fair, but when you determine at what rate the interest should be paid, there is a good question as to whether it should be paid at the treasury bill rate, at the treasury bill rate plus 2%--which is what it was before for corporations--or at the treasury bill rate plus 4%. Previous to that, it was the treasury bill rate plus 2% for all taxpayers. Now for individuals it stays at the treasury bill rate plus 2%, but for corporations it's what the corporation would get had it invested straight up in a treasury bill.
On April 22nd, 2010. See this statement in context.