Unable to update address as unable to set up Gateway account or speak to a human.

I have been trying to help my father-in-law update his address, as correspondence about his tax code went to his old address at the start of this year. My wife tried repeatedly to navigate the automated phone line and was only able to get a link to the gateway service sent by the automaton. She was hoping to get through to a person that he could speak to but was unsuccessful. He is unable to set up a gateway account as he does not have the required ID documents. How can he update his address please?

Hi,
If you've had trouble contacting us directly by phone, you can contact us by webchat:
Income Tax: general enquiries and click 'Ask HMRC online'.
Alternatively,  update us by post, by writing to us at the address given on the link above.
Thank you.