Hi Akhilesh,
You can tell HMRC you’re leaving through your tax return, if you still have one outstanding.
Complete the ‘resident’ section (form SA109) and send it by post.
If you've already told us that you've left the country, your record is most likely already closed, but please contact us by webchat or post here:
Self Assessment: general enquiries
To confirm this, and also to allow us to advise on any income you may still be due to pay UK tax on.
Thank you.