If you do not agree with an assessment, a disallowance or a decision issued by the Ministry of Finance, there may be a simple solution to your problem. Informal discussions solve many disagreements and misunderstandings about tax and benefit program decisions. Therefore, contact the ministry first to discuss your particular situation.
If you still disagree, you do have the right to send a Notice of Objection to the Objections and Appeals Branch. The publication Ontario Taxes and Programs: Objection and Appeal Procedures provides complete details about the objection and appeal process.