HMRC offers several separate routes for helping a relative with their tax, and each needs a different kind of authority. A trusted helper can manage a relative’s Income Tax online for 90 days, an intermediary authorised by letter can talk to HMRC and help with forms, and someone with a registered lasting power of attorney or a deputyship can make decisions for them. Whichever route you use, your relative stays legally responsible for their own tax.

Which route fits your situation?

The right route depends on what you need to do and whether your relative can still make their own decisions. HMRC’s guide Appoint someone to deal with HMRC on your behalf sets out the options.

Route Authority needed What it allows Main limits
Trusted helper Online registration by you, accepted online by your relative within 28 days Checking Income Tax, the personal tax account, company car and medical benefits, State Pension and National Insurance record Lasts 90 days; no Self Assessment
Phone call together Your relative confirms on the call that they are happy for you to speak Discussing any tax issue You must be in the same room
Intermediary Signed letter from your relative Talking to HMRC and helping fill in forms No access to their tax online
Power of attorney or deputyship Registered lasting power of attorney, or a Court of Protection order Making tax decisions for them or helping them decide Must be registered with HMRC
Paid agent Agent authorisation online or on form 64-8 Dealing with their tax affairs, such as filing returns Agent must meet HMRC’s standard

How does the trusted helper service work?

You register online as a trusted helper and your relative then uses the service to accept your offer within 28 days. Once accepted, you can help with their tax online for 90 days, after which you must register again. You can be a trusted helper for up to five people. You will need your own sign in details and may have to prove your identity, normally with photo ID.

A trusted helper can check that your relative is paying the right amount of Income Tax, check or update their personal tax account, check or update taxable benefits (company cars or medical insurance only), check their State Pension and view their National Insurance record. That makes it useful for queries such as a wrong PAYE tax code on a pension or a P800 calculation. It cannot be used for Self Assessment, and it gives you no legal power to make decisions.

How can you speak to HMRC without online access?

If your relative cannot go online, you can phone HMRC on their behalf about any tax issue as long as you are in the same room. HMRC will confirm their identity and check that they are happy for you to represent them, and you need their National Insurance number or tax reference. If you are interpreting for someone who does not speak English, you must be over 16. For short term help with Self Assessment, HMRC says to call with the person present.

For a longer arrangement, your relative can authorise you as an intermediary. HMRC suggests this where someone is ill, has a disability or does not speak English. They write to HMRC at National Insurance contributions and Employers Office, HM Revenue and Customs, BX9 1AN, giving their name, address, date of birth, tax reference such as a Unique Taxpayer Reference, your name and address, and their signature. An intermediary can talk to HMRC and help with forms but cannot see the account online.

What changes once you hold a lasting power of attorney?

A lasting power of attorney (LPA) is made by the donor while they still have mental capacity and must be registered with the Office of the Public Guardian before it can be used. Only a property and financial affairs LPA is relevant to tax. It can be used as soon as it is registered, with the donor’s permission, so it does not need to wait until capacity is lost. A health and welfare LPA cannot be used for tax. An LPA is legally binding only in England and Wales; Scotland and Northern Ireland have their own powers of attorney.

Holding the LPA is not enough on its own: HMRC needs to know about it. There are two ways to tell HMRC.

  • By phone. This works if the LPA was registered on or after 1 January 2016 in England or Wales, you have an LPA online account and you can make property and financial decisions. You call the relevant helpline and give a 13 character access code from your LPA account. Codes can only be given by phone. HMRC may still ask for an original or certified copy.
  • By post. Send the original or a certified copy to Pay As You Earn and Self Assessment, HM Revenue and Customs, BX9 1AS (or to Benton Park View, Newcastle upon Tyne, NE98 1ZZ if you are outside the UK). The document is returned, and you should not need to send it again unless the details change.

Once HMRC has updated its records, it can discuss your relative’s tax with you. Remember that an attorney’s powers to make gifts are limited; see gifts made by an attorney.

What if there is no power of attorney?

If your relative has already lost capacity and never made an LPA, someone can apply to the Court of Protection to become their property and financial affairs deputy. The court order sets out what the deputy can do, and deputies must send an annual report to the Office of the Public Guardian. Once appointed, a deputy can manage the person’s tax affairs. Scotland uses guardianship and Northern Ireland uses controllers instead of deputies. If you only need to manage someone’s benefits, GOV.UK says you can apply to be an appointee rather than a deputy.

Who signs your relative’s tax return?

HMRC’s Statement of Practice A13 says the declaration on a return is a duty the taxpayer cannot delegate, so HMRC’s normal practice is to insist on a personal signature. It recognises that age or physical infirmity can make this impossible and says it will consider such cases sympathetically and, where possible, accept the signature of an attorney who has full knowledge of the taxpayer’s affairs. In practice, tell HMRC about the power of attorney before you file.

Making Tax Digital for Income Tax has a specific exemption. Under the rules summarised at SALF1480, the digital obligations do not apply to the donor of an LPA or enduring power, or a person with a deputy, unless the power has been revoked or has ended, or, for a power of attorney, the donor can still provide financial information to HMRC. See MTD for Income Tax exemptions.

When should a professional agent take over?

If your relative has a business, rental income or complicated affairs, a paid accountant or tax adviser may be more suitable. Agents must meet HMRC’s standard for agents and are normally authorised online; where that is not possible, form 64-8 is used. Being authorised does not transfer the client’s legal obligations to the agent. If your relative has a Self Assessment return, HMRC sends correspondence to the authorised person except tax bills and refunds. After a death, personal representatives can use form 64-8 to authorise an agent for the estate; see tax returns for someone who has died.

A worked example

Illustration only. Alan, aged 84, has a State Pension and two small occupational pensions. His daughter Ruth notices one pension is taxed on an emergency code. Alan can still make decisions but finds phone menus hard. Ruth registers as his trusted helper, Alan accepts online with her help, and Ruth checks his tax code and asks HMRC to correct it. Two years later Alan’s memory declines. He had made a property and financial affairs LPA in 2019, registered that year. Ruth uses her LPA online account to get an access code, calls HMRC to register the LPA, and from then on can deal with HMRC on his behalf without the 90 day limit.

What mistakes do families make?

  • Posting an ordinary photocopy of the LPA. HMRC needs the original or a certified copy.
  • Assuming a trusted helper can deal with Self Assessment. It cannot.
  • Forgetting that trusted helper access ends after 90 days.
  • Relying on a health and welfare LPA, or an unregistered LPA, for tax.
  • Not telling HMRC about the LPA, so calls are refused even though the power is valid.
  • Thinking the helper becomes liable. The person being helped remains legally responsible for their own tax.

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Sources

Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 19 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.