Once your Income-tax return is submitted, you get the acknowledgement copy (ITR-V) having unique acknowledgement number. You get this copy on e-mail once your return is filed. Also, it is available to download in your Income-tax portal login.
Below is the process to check the acknowledgement number:-
Step 1: Sign in to the Income-tax Department website. Click here
Step 2 : Click on View Filed returns under e-File tab
e-File>>Income Tax Returns>> View Filed Returns
Step 3: You will get the acknowledgement number under the relevant AY and also option to download ITR-V copy (receipt).