The income tax department has served notices on a set of Tata trusts, seeking to reopen assessment and questioning their decision to ‘surrender’ registrations in 2015. The department, which sent the notices last month, is seeking to tax the accumulated income of the trusts for certain years. The department believes the trusts were not in a position to ‘surrender’ their registrations, which can only be ‘cancelled’ by the tax office, three persons familiar with the matter told ET. According to Section 115 (TD) of the Income Tax Act, a trust whose registration is cancelled is required to pay tax on its accumulated, or ‘accreted’, income. In this case, the tax will amount to at least Rs 1,800 crore, after considering the fair market value of the trusts’ total assets net of liabilities.