How to notify HMRC of a power of attorney

Can I notify HMRC of my power of attorney through the Government portal Gov One uk

Hi,
Please use the link below for advice about registering a power of attorney:
Appoint someone to deal with HMRC on your behalf
Thank you.

The following is an extract from the above link. Once the person helping you has a registered power of attorney, they will need to tell HMRC so they can update their records. Tell HMRC about the power of attorney by phone The person helping you can tell HMRC by phone if all of the following apply: the LPA was registered on or after 1 January 2016 in England or Wales they have an LPA online account they can make decisions about property and financial affairs The person helping you will need to contact the relevant HMRC helpline. For example, they need to call the National Insurance helpline if they’re calling about National Insurance contributions. When they call, the person helping you will need to give HMRC an access code so they can check that the LPA is valid. To get an access code, the person helping you will need to sign in to their LPA online account. Access codes are 13 characters long and start with a V, for example, V-AB12-CD34-EF56. Access codes can only be given over the phone, they cannot be sent by post After I phone the HMRC helpline they say this is not possible and they cannot accept the code over the phone please explain why?

Hi,
I am sorry but if you contact HMRC with the details of the code the LPA should be able to be traced. 
Income Tax: general enquiries
Thank you.

Please take care with your next steps. I did finally get an hmrc call handler to go through an extremely longwinded process (that they were clearly unfamiliar with) to view the code I'd generated and accept that I was a valid POA for my father. Unfortunately after all that they then said I couldn't do anything related to my father's tax affairs unless I sent in the original copy of the POA document, which seems to make the whole code system pointless. Having sent the original POA by registered post next day delivery and called back multiple times, I have since been given increasingly longer timeframes for the document to be acknowledged as received and attached to my fathers records and then arranged to be returned. Had I known the lengthy timeframe or had any explanation of an actual coherent process for all this, I would not have sent it as it is needed elsewhere. I would've arranged to have made a certified copy and sent this instead but was told the original was needed. Maybe you will have more luck being able to act with just the code, but if not and you have to send the POA document, I recommend you send a certified copy only. Can you publish how you get on here? Good luck