The municipal tax bill on the premises your business occupies is a business expense. On Form T2125, it goes on line 9180, Property taxes.
What belongs here
Property taxes you incurred for property used in your business — for example, the property taxes for the land and building where your business is situated.
What does not belong here
The property tax on your home. If you work from a workspace at home, that part of the tax has to be claimed as business-use-of-home expenses, in the home-office part of the form. It is worked out as a share of the whole bill, which is a calculation rather than a separate document.
What to keep
Keep a record of all your income and expenses, with the documents behind them. For this line, keep the municipal tax notice or bill: it names the property and the year, which is what ties the amount to the premises your business uses.
Don't send it in with your return. Keep it in case the Canada Revenue Agency (CRA) asks to see it. Business records follow the same six-year retention rule as your personal documents.
Official CRA sources
Source: Canada Revenue Agency (canada.ca). Not tax advice.