Enforcement Act of Land Act Article 48

When taxable land becomes tax-exempt land, the land tax shall be remitted starting from the year the tax-exempt status is granted. However if the land has not been used on the basis of the reason for granting tax-exempt status, the land tax thereon shall not be remitted.
中文原文 土地法施行法第48條
稅地變為免稅地時,其土地稅自免稅原因成立之年免除之。
但未依免稅原因使用者,不得免稅。

English translation for reference only; the Chinese text prevails. Not legal advice.