HMRCforumqueries

I am an executor of a relative who may have dividends above the dividend allowance that may not have been reported. I expect the annual total of dividends is below £10,000. How many tax years do I have to go back through from the date of death. Is it the three tax years previous to the year of death? And if there is some tax due from these earlier years, when is the due date for the tax charge and when will interest on overdue tax start to run from?