The Central Board of Direct Taxes (CBDT) on Tuesday issued updated guidelines for referencing computer-generated Document Identification Numbers (DIN) in income-tax communications. It states that any correspondence such as notices, letters, orders, draft orders, or summons issued by income-tax authorities to taxpayers must reference a DIN. The circular also lists practical exceptions where DIN referencing may not be possible, including technical difficulties, field enquiries outside the office, or system unavailability. In such cases, the communication must explicitly state the reason and require post-facto approval within 15 days by a competent authority.