I think what you're trying to get at is there are situations that occur on a regular basis where people try to avoid paying tax. In those circumstances, the Department of Finance or the Canada Revenue Agency become aware of that, not through the technical process, but through other processes we have to identify the things that will result in revenue loss for the government.
When we find those things, we normally take action as quickly as possible. A number of examples are on the tax-free savings account. Some people figured out ways to put more money into tax-free savings accounts than should have been put in there. As soon as we identified the issue, we put out a press release saying that we had identified the issues and were going to propose legislation to Parliament to prevent these things from taking place. We normally have effected those things on the day of the announcement, on the day of the press release. We then hope Parliament will agree to pass the legislation effective on that date.
Sometimes things are so egregious that it becomes retroactive. We sometimes say it's so bad that we have to stop it retroactively. We're trying to maintain a balance. When taxpayers don't have the information to know what the law would have been two years ago, how can they comply with those laws? We try to balance fairness to the taxpayer and protection of the revenue base. In some cases, it's effective on the date of the announcement. When it's really egregious, we sometimes go back in time as well.