Client Onboarding Best Practices for Accountancy Practices

The Accounted Business Team·3 March 2026·7 min read

The first thirty days of a client relationship set the tone for everything that follows. Get onboarding right, and you have a client who understands what you need from them, provides information on time, and stays with you for years. Get it wrong, and you spend months chasing missing records, managing confused expectations, and eventually losing the client to a practice that made them feel looked after from the start.

A well-structured onboarding process isn't just good client service. It's one of the most effective ways to reduce churn, improve efficiency, and protect your practice's margins. Here's how to build one that works.

Why Onboarding Matters More Than You Think

Research across professional services consistently shows that client retention is strongly linked to the quality of the onboarding experience. In accountancy, the numbers are particularly telling:

Practices with structured onboarding report client retention rates 20% to 30% higher than those without
The most common reason clients leave an accountancy practice in the first year is feeling "neglected" or "confused about the process"
The cost of replacing a lost client (marketing, sales conversations, setup time for the replacement) is typically three to five times the cost of onboarding them properly in the first place

The pattern is clear. Clients who feel well-managed from day one stick around. Those who feel like they've been thrown into the deep end start looking elsewhere.

The Onboarding Checklist

Every new client, whether they're a sole trader, landlord, limited company director, or partnership, needs a structured set of steps completed before you can serve them effectively. Here's a comprehensive checklist.

1. Engagement Letter and Terms

Before any work begins, issue a formal engagement letter that covers:

The services you'll provide (bookkeeping, Self Assessment, VAT returns, payroll, advisory, etc.)
What's included in the fixed fee and what attracts additional charges
Your responsibilities and the client's responsibilities
Data protection and confidentiality terms
Your complaints procedure
Termination terms

Don't skip this step, even for referrals from existing clients. An engagement letter protects both parties and sets expectations clearly. It's also a regulatory requirement for practices regulated by professional bodies.

2. Anti-Money Laundering (AML) Checks

All accountancy practices must carry out client identification and verification under the Money Laundering Regulations. For each new client, you need:

Proof of identity (passport or driving licence)
Proof of address (utility bill or bank statement, usually less than three months old)
For companies, verification of the company and its beneficial owners
For trusts, identification of trustees and beneficiaries

Complete AML checks before starting any work. Document everything and keep it on file. This is a legal requirement, not a nice-to-have.

3. Document Collection

Gather the baseline documents you need to understand the client's financial position:

Previous year's tax return (or the last two to three years if available)
Previous year's accounts
VAT registration details and recent VAT returns (if applicable)
PAYE scheme details (if applicable)
Corporation Tax computations (for limited companies)
Details of any ongoing HMRC correspondence, enquiries, or disputes
Current bank statements
Details of any loans, hire purchase agreements, or leases
Insurance policies relevant to the business

4. Agent Authorisation

To deal with HMRC on the client's behalf, you need to be authorised as their agent. This involves:

Self Assessment: The client authorises you through their HMRC online account, or you submit a 64-8 form
Corporation Tax: Authorisation through the company's HMRC online account
VAT: Separate agent authorisation for VAT, especially important for MTD
PAYE: Agent authorisation for the PAYE scheme if you're handling payroll

Agent authorisation can take several weeks to process if done by post. Start this on day one.

5. Bank Access and Feed Setup

Modern accountancy relies on bank feeds. Set up connections to the client's business bank accounts so transactions flow in automatically. This typically involves:

The client logging into their bank through the accounting software's Open Banking connection
Authorising the read-only data feed
Verifying that historical transactions have imported correctly

If the client uses multiple bank accounts, credit cards, or payment processors (like Stripe or PayPal), set up feeds for all of them.

6. Software Migration

If the client is moving from another accounting package, you need to migrate their data. This includes:

Chart of accounts mapping
Opening balances (trial balance as at the migration date)
Outstanding invoices and bills
Fixed asset register
VAT scheme details

A clean migration is essential. Errors in opening balances create problems that cascade through every subsequent period. Take the time to reconcile the migrated data before moving forward.

7. Expectations Setting

This is the step most practices skip, and it's the one that matters most for retention. Sit down (or have a video call) with the client and cover:

What you need from them and when: Receipts within a week of purchase, bank access maintained, queries responded to within a set timeframe
What they can expect from you and when: Monthly reports by a specific date, tax returns filed by a specific deadline, availability for questions
Communication preferences: Do they prefer email, phone, WhatsApp, or app notifications?
Key deadlines: Walk through the tax calendar for their specific situation. When are VAT returns due? When is Self Assessment due? When do quarterly MTD submissions happen?
How fees work: When they'll be invoiced, what payment methods you accept, what happens if additional work is needed

Common Onboarding Mistakes

Trying to Do Everything at Once

Don't overwhelm the client with requests on day one. Prioritise the essentials (engagement letter, AML, agent authorisation, bank feeds) and phase in the rest over the first two to four weeks. A structured timeline with clear milestones is easier for the client to follow than a single massive checklist.

Not Assigning a Point of Contact

Clients need to know who to contact with questions. If they don't have a named person, they either contact everyone or no one. Assign a primary contact from the start, even if multiple team members will work on the account.

Failing to Chase Missing Items

It's common for clients to provide most of what you need but forget one or two items. If you don't follow up promptly, those missing items become a permanent gap. Set reminders to chase anything outstanding within a week of the initial request.

Skipping the Software Tour

If your practice uses client-facing software (a portal, app, or messaging tool), walk the client through it. Don't just send a login link. A five-minute screen share showing them how to upload receipts, view their accounts, and respond to queries prevents weeks of confusion later.

Not Reviewing the Previous Accountant's Work

Always review the last set of accounts and tax return before you start. You might find errors, missed deductions, or structural issues that affect your work going forward. It also helps you understand the client's business before your first advisory conversation.

Onboarding for MTD Clients

With Making Tax Digital for Income Tax starting from April 2026, onboarding is about to get more involved. New clients who are within the MTD threshold need:

MTD-compatible software set up and connected to HMRC
Digital record keeping established from day one
Quarterly submission schedules agreed and calendared
An explanation of how MTD differs from annual Self Assessment

Practices that build MTD readiness into their standard onboarding process now will avoid a scramble when the deadline hits. Clients onboarded onto MTD-ready software today are clients who won't cause you problems in April.

Accounted's Built-In Onboarding Workflow

Accounted includes a structured onboarding workflow designed specifically for accountancy practices. When you add a new client to your practice portal, the system guides you through each step:

A digital engagement letter workflow with e-signature
AML check prompts and document storage
Automated bank feed connection through Open Banking
Guided data migration from Xero, QuickBooks, FreeAgent, and spreadsheets
A client-facing welcome message from Penny, Accounted's AI bookkeeper, that explains how the system works, how to upload receipts, and what to expect

Penny takes over the day-to-day bookkeeping from the moment the bank feeds are connected. She categorises transactions, chases receipts from the client via WhatsApp, and flags exceptions for your review. By the time you sit down to review a new client's first month, the heavy lifting is already done.

The result is that onboarding a new client takes hours, not weeks. And because the process is consistent, every client gets the same professional experience, regardless of which team member handles the setup.

Make Onboarding Your Competitive Advantage

A smooth onboarding experience doesn't just reduce churn. It becomes a selling point. When prospective clients hear that your practice has a structured, technology-supported onboarding process that gets them set up in days rather than weeks, it differentiates you from practices still relying on email chains and paper forms. Start your free trial of Accounted today and see how a streamlined onboarding process transforms your practice's first impression.

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