A client onboarding checklist for small UK accountancy practices

The gap between a client saying yes and that client being properly set up is where a lot of practice time disappears. Nothing in it is difficult. It is a dozen small requests, each waiting on the client, and the risk is that work starts before the essentials are in place.

Here is a checklist for a small practice taking on a sole trader, landlord or small company, in the order that usually works. Your own procedures, and your supervisory body’s guidance, come first.

1. Engagement letter, on the day they say yes

Send the engagement letter and terms straight away, while the client is keen. ICAEW fully updated its engagement letter helpsheet and templates in March 2026, the first full review since 2023. The update added schedules on identity verification, filing company accounts for clients and Making Tax Digital services, and the terms of business now cover the use of AI and other software tools in delivering the service.

If your letters pre-date that update, it is worth comparing them, particularly if you use any AI or automation tools with client data.

2. Customer due diligence for anti-money-laundering

Under the Money Laundering Regulations, you need to identify and verify the client, and understand the nature of the work, before the business relationship gets going. The accountancy sector’s guidance (AMLGAS, prepared by the CCAB bodies) was reissued in 2026 to reflect the law as at 1 July 2026, including amendment regulations that took effect on 30 June 2026. According to the summaries from ACCA and CIOT, the update covers customer due diligence, including sources of evidence and digital verification services, and enhanced due diligence. The amendments also converted several monetary thresholds from euros into sterling, so check your checklists still state them correctly.

In practice, collect:

• photo ID and proof of address for the individual, or for the directors and people with significant control of a company;
• what the client does and where their money comes from, at the level your risk assessment needs;
• your risk assessment and what you checked, recorded on the file.

Collecting documents can be delegated or automated. The judgement on whether due diligence is complete stays with the practice.

3. Professional clearance from the previous accountant

If the client had an accountant before, ask for their details early and send the professional clearance request. Replies can take time, and the handover information (outstanding returns, payment arrangements, agent codes) often decides what you do first.

4. HMRC authorisations

Request the authorisations you need through your agent services account. For Making Tax Digital for Income Tax, the client has to accept the request online. This is the item most likely to stall: the client gets an email from HMRC they don’t recognise and leaves it. Tell them in advance what it will look like, then follow up until it is accepted.

5. Companies House identity verification, for company clients

Identity verification became mandatory for new directors and people with significant control from 18 November 2025. Existing directors verify at the company’s next confirmation statement, during a 12-month transition that ends in November 2026. If any director hasn’t verified, the confirmation statement can’t be filed. For a new company client, check where each director and PSC stands as part of onboarding rather than discovering it at the confirmation statement.

6. Making Tax Digital readiness

For sole traders and landlords, confirm whether they are in scope now or will be from April 2027 (qualifying income over £30,000) or April 2028 (over £20,000), which software they will use for digital records, and how their bank feeds will connect. See our Making Tax Digital summary for the dates.

7. Software and access

Set the client up in your practice and accounting software, connect bank feeds, and agree how they will send documents to you. One agreed route (for example, reply to one address) saves hours of sorting later.

8. Welcome pack, last

Once the essentials are in, send a short welcome: who their contact is, what you will ask for and when, and how to reach you. It sets the rhythm for every reminder that follows.

Keep one view of where each client is

The checklist itself is not the problem. Keeping track of eight items across five new clients, each waiting on someone else, is. A single view per client (done, waiting, needs a person) is what stops a new client sitting half set up for a month.

That is what Onboarding Desk does: it sends your letter, collects the documents, keeps the authorisation moving and works through your checklist, with your team approving messages and verifying documents. To talk through how onboarding works in your practice, suggest a time.