What document is vital for determining a non-resident seller's tax obligations in Canada?

The correct answer is C. Income Tax Act. This document is vital for determining a non-resident seller's tax obligations in Canada because the Income Tax Act sets out the rules and regulations regarding taxation, including how taxes are applied to non-residents selling property in Canada. It is important to consult the Income Tax Act to understand the tax implications and obligations as a non-resident seller.

Options A, B, D, E, and F are not directly related to determining a non-resident seller's tax obligations in Canada. A Residency Certificate may be important for proving residency status but is not directly related to tax obligations. The Sales Contract, Title Deed, Transfer of Land Form, and Property Valuation Report are all important documents in a real estate transaction, but they do not specifically determine a non-resident seller's tax obligations.