... and pay for the privilege ...
Being a partnership, we have to pay for "software" (actually an editable pdf form) to submit our return as there is no online version on the HMRC site.
The HMRC pages seem to be designed for them rather than the user, e.g. when doing our individual returns, at the beginning there are questions about whether you are employed as we as self-employed. Despite saying no, half-way through the form it asks if you want tax collected by PAYE (from a non-existent job).
There are also links that give 404s (not in the actual form)
When online filing first started, there was an error relating to charitable donations. The Tax office said there was a "quirk in the system". One of our sons suggested that this might Microsoft Quirk.
Send them a message? But don't use the wrong characters or carriage returns - but you don't get told this until after you've tried sending it, and it doesn't like pages referenced by URLs either.
They did reply to a question about the VAT pages -tried to find out why an old post code was shown but not allowed to access "my account". They said:
"I advise that you contact our helpdesk on the telephone number below as the ‘access denied’ error message that you detailed in your email may be linked to the ‘shared secret’ security questions on your account which may need to be cleared by an advisor after completing security"
So there! Except that no "shared secret" question had been asked.