Receipt confirmation for self assessment sent by post

Hi, I had sent Self-Assessment report via postal mail (as I'm not a UK resident). The mail service includes an SMS receipt notification, which usually arrived within 2 weeks. But this time - a month passed and nothing. Please note that I'm not expecting a reply but an indication for my mail arrival. How can I check that the report indeed arrived at HMRC? Thank you

Hi

You can contact our Self Assessment department by webchat clicking the 'ask HMRC Online' link and asking to speak with an adviser.
We will then check if it has been received.

Thank you