New client checklist for accountants: what to collect before you start

Most practices collect the same things from every new client, but ask for them in dribs and drabs: the engagement letter in one email, ID in another, the records when the deadline is close. The client answers some, forgets the rest, and the gaps only show up when the work starts.

A written checklist fixes the order. The items below are grouped into what you need before you can act, what you need to meet your own obligations, and what the first piece of work needs. Send it as one list and the client can work through it in an evening.

• Professional clearance. If the client had an accountant before, your professional body expects you to write to them asking whether there is any reason you should not act, and for the records you need to pick things up. Ask the client for the previous firm’s name and contact, and permission to write to them. This often takes longest, so ask on day one.
• A signed engagement letter. It sets out what you will do, what you won’t, your fees and how either side ends the arrangement. Nothing should start until it is signed. An electronic signature is fine for an engagement letter; see are electronic signatures legal in the UK?.
• Authority to deal with HMRC. For Self Assessment, Corporation Tax, VAT and PAYE you need the client’s authorisation as their agent. HMRC offers a digital request the client approves through their Government Gateway account, or the paper form 64-8. See HMRC’s overview of client authorisation. Ask for their Unique Taxpayer Reference (UTR) and, for individuals, their National Insurance number, so the request goes through first time.
• The Companies House authentication code for a limited company, if you will file on their behalf. The client can find or request it from their Companies House account. See Companies House on authentication codes.

Accountancy firms are supervised under the Money Laundering Regulations 2017 and must carry out customer due diligence before starting work: identify the client, verify who they are, understand what the business does and assess the risk. The Money Laundering, Terrorist Financing and Transfer of Funds Regulations 2017 set the duty; your supervisory body’s guidance says how to meet it. ICAEW’s notes on due diligence for new clients list the most common gaps its reviewers find.

What practices commonly ask for:

• Photo ID for the client, or for a company the key contact and, depending on risk, the directors: a passport or another government photo document.
• Proof of address dated within the last three months, such as a bank statement or utility bill.
• For a company or partnership, who the beneficial owners are. Check the people with significant control at Companies House and ask the client to confirm the list is current.
• What the business does and where its money comes from, in a few sentences. For higher-risk clients you may need evidence of source of funds; for most small businesses you won’t.

Separately, since 18 November 2025 directors and people with significant control have had to verify their identity with Companies House, with a transition period for existing officers. A firm registered as an authorised corporate service provider can verify clients for this. It is a different check from your own due diligence, so don’t treat one as covering the other. See Companies House on identity verification.

Ask for what the first job needs and leave the rest. A long list on day one is the surest way to get nothing back. Commonly asked for, by client type:

• Sole trader or landlord: last year’s tax return and computation if another firm prepared it, business bank statements for the period, sales invoices or takings records, expense receipts, mileage log, and for landlords the letting agent statements and mortgage interest statements.
• Limited company: the certificate of incorporation and company UTR, last filed accounts and Corporation Tax return, bank statements for every business account, sales and purchase ledgers or the bookkeeping software login, payroll records and PAYE reference, VAT number and the last return, dividend vouchers and any director’s loan movements.
• Anyone switching from bookkeeping software: accountant access to the software rather than exports, so you can see the live position.

If the client will be in Making Tax Digital for Income Tax, say now that you will ask for records each quarter, and keep the first request to the year you are working on.

In the order to ask:

1. 1A short details form: legal name, trading name, address, date of birth or incorporation date, UTR, National Insurance number or company number, VAT number, year end, previous accountant.
2. 2Photo ID and proof of address for the people you need to verify.
3. 3Your engagement letter, to sign.
4. 4HMRC agent authorisation, approved through their Government Gateway, and the Companies House authentication code if you will file.
5. 5The records for the first job, from the lists above.
6. 6One open question: “Anything else we should know?”

Put a date on each request that has one, and tell the client what happens once it’s all in. The same list, with your wording, is what you send to every new client from then on.

1. 1Build the list above once as a checklist: a form for the details, an upload for each document, and your engagement letter as a contract the client can sign online.
2. 2Send it to the new client. They get one link, sign in to your branded portal and work through the items on their phone or laptop.
3. 3Switch on an AI check for the uploads that usually come back wrong, with your own wording, such as “a bank statement covering the whole accounting year, with the account name showing”. The client sees the result as soon as they upload, so they can fix it then.
4. 4Watch what is in, what needs a look and what is still missing from the client’s page, and send a reminder when you choose.

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