This is the single most valuable thing to understand about losing a job in Canada: there are two separate entitlements, and most people only know about one.
Statutory notice
Employment standards legislation sets minimum notice periods, ranging from about one week to eight weeks depending on the province and your length of service.
Your employer can provide working notice or pay in lieu — ending the job immediately and paying a lump sum covering the period.
Common-law reasonable notice
Here is the part that matters. Statutory notice is a minimum requirement — the floor, not the ceiling.
Where an employment contract does not properly limit termination entitlements, common-law reasonable notice applies instead, and it is almost always higher.
Courts assess reasonable notice on factors including your age, length of service, the character of the position and the availability of similar employment.
The contract clause that decides it
Employers with properly drafted employment contracts can limit termination pay to the statutory minimums.
Without such a clause — or where the clause is defective and fails to meet statutory standards — common-law notice applies.
This is why the termination clause in your contract is worth reading before you sign, and worth having reviewed if you are terminated.