Cannot access or reset authentication method of my Self Assessment Account

I am writing to seek assistance with an issue I am experiencing with my Self Assessment account. Currently, I am unable to access or reset the authentication method for my account. The problem began because I no longer have access to the authenticator app that was initially used to set up my account. I have called support multiple times for assistance, but unfortunately, they were unable to verify my identity. As a result, I am now stuck and unable to manage my Self Assessment tax account directly. This situation has forced me to rely on third parties to pay my Self Assessment tax, which is not ideal and causes significant inconvenience. Could you please advise me on the steps I need to take to regain access to my account or reset the authentication method? Your prompt assistance in resolving this matter would be greatly appreciated. Thank you for your help.

Hi,
For assistance you will need to contact our Online Helpdesk:
Technical support with HMRC online services
Thankyou.

I have exactly the same issue, The online helpdesk are unable to help as I cannot provide them with the information stored within my personal tax account in order to remove the authenticator app from the tax account as a method of receiving the verification code. Deadline is approaching and I have no way of submitting my self assessment as apparently my passport is not sufficient identification, I need to be able to provide the month & year I first registered for self assessment and the month and year of my last submission, both of which are pieces of information I only have stored in my personal tax account which I cannot gain access to. Calling the online helpdesk again is not going to help so what should I do? Incredibly frustrating.

Hi,
To see if there is alternative information you can provided to verify your identity you will need to contact the online helpdesk.
Technical support with HMRC online services
If you are unable to verify your identity then you will not be able to file the Self Assessment online and a paper tax return will be needed.
Self Assessment tax return forms
Thank you.