If you don't file your Income Tax Return (ITR) by the due date, several consequences can arise:

• You may have to pay a late filing penalty under Section 234F. The penalty is Rs. 1,000 if your income is up to Rs. 5 lakh and Rs. 5,000 if your income exceeds Rs. 5 lakh.
• Interest under Section 234A will be charged at 1% per month on the outstanding tax amount from the due date till you file the return.
• You will lose the benefit of carrying forward certain business or capital losses to future years, which can increase your future tax liability.
• Your tax refund processing may be delayed or rejected due to non-filing.
• Non-filing can make it difficult to provide proof of income needed for loans, visas, and other financial matters.
• Persistent failure to file may lead to legal action, including prosecution and imprisonment if the tax department considers it to be tax evasion.

You can still file a belated return after the due date but it comes with penalties and interest, and the final deadline for filing belated returns is December 31 of the relevant assessment year. Thus, not filing your ITR on time can lead to financial penalties, interest, loss of tax benefits, delays in refunds, and even legal troubles.