It depends on the municipality, but it could result in a heavy fine. In some cases, it could also result in jail time. Generally, the fines will be based on the value of the structure that was built without a permit. For example, in Toronto, the fine for building without a permit is $50 per day for each day that the structure is not compliant with zoning by-laws. So, if you build a structure that's worth $5,000 and it takes 10 days for you to get a permit, you would be fined $500 (10 x $50).
It depends on the municipality, but generally speaking, the fine for building without a permit is pretty steep--usually in the thousands of dollars. Building without a permit is illegal for a reason: it can endanger the public and/or structurally compromise the building. Not only will you have to pay a hefty fine, but you may also have to tear down what you've built and/or face legal action. So it's not worth taking the chance--get that permit!
