It is the best practice.

Here are few reasons:

• To avoid Tax Credit Mismatch. This is the most common error found nowadays resulting in less refunds or additional tax liabilities.
• To avoid escapement of any income declaration in ITR. E.g. PF withdrawal if it’s taxable as it is in some cases and TDS is been deducted on it, FDR interest.
• Income Mismatch in case of Salary income. Strong chances of ITR to be termed as Defective u/s 139(9) of income tax act, 1961. As salary income declared in ITR is less than salary income as per 26AS.
• Also, 26 AS Statement shows us any AIR transactions reported by various authorities to ITD. E.g Purchase of mutual funds of amounts exceeding Rs.2 lakhs or total amount deposited in savings bank account exceeding Rs. 10 lakhs.