Charitable Trust : How Taxed If Lost Exemption u/s 11 & 12 ?

We all know that the charitable trusts get the tax exemption under section 11 and section 12 . So , if charitable trust is not bothered about taxation part. But once , for various reason , a charitable trust losses the tax exemption , the taxation of income of a charitable trust becomes a complex issue. A premium subscriber has asked a question on the taxation issue of a charitable trust which has not been registered under section 12A read with Section 12AA of the Income Tax Act. So, here is the simplification of the taxation aspect of a charitable trust if it losses exemption