A clean onboarding for a new UK accounting client takes a few hours of work spread over five to ten working days and follows a repeatable sequence: discovery call, professional clearance from any predecessor, AML and KYC checks, engagement letter, agent authorisations, software access, kick-off, and a clear handover of who-does-what going forward. Standardising this process is one of the highest-leverage things a small practice can do.
Why onboarding matters
Onboarding sets the tone of the relationship, reduces compliance risk, and removes friction from the first month of work. A loose onboarding leads to scope confusion, missed information, and a slow path to revenue. A tight onboarding gets you billing on a clear contract within two weeks and protects you when something goes wrong later.
The onboarding sequence
- Discovery call (30 to 45 minutes): understand the client's structure, services needed, current accountant, deadlines, software, and pain points
- Proposal: send a written proposal with services, scope, fees, and packages
- Acceptance: client agrees in writing, e-signature ideal
- Professional clearance: write to the predecessor accountant requesting clearance and handover information
- AML and KYC: collect ID and address verification, beneficial owner identification, source of funds, complete client risk assessment
- Engagement letter: issue your standard letter plus service-specific schedules; collect e-signature
- Agent authorisations: HMRC agent authorisations for each service (corporation tax, self-assessment, PAYE, VAT) via Agent Services Account; Companies House Authentication codes
- Software access: connect to the client's bookkeeping software, set up bank feeds, receipt-capture apps, payroll software
- Direct debit setup: GoCardless or Stripe mandate for monthly fees
- Information handover: collect any documents from the predecessor; update permanent file with statutory records
- Kick-off call: confirm what happens next, who-does-what, and key dates for the next 90 days
- Welcome: a written welcome email with key contacts, response times, and useful links
AML at onboarding
AML is the most critical step. It includes:
- Verifying identity for every individual client and beneficial owner
- Verifying address (utility bill, bank statement, or electronic ID equivalent)
- Identifying beneficial owners of corporate clients (typically those with 25%+ ownership or control)
- Documenting the purpose and intended nature of the business relationship
- Assessing client risk (low, standard, high) using your firm risk assessment
- Applying enhanced due diligence (EDD) for higher-risk clients (PEPs, complex structures, high-risk jurisdictions)
Use an electronic ID verification service (e.g. SmartSearch, Veriphy, Credas) to speed up checks. Keep records for at least five years from the end of the relationship.
Agent authorisations
You need separate agent authorisations for each HMRC service:
- Corporation tax: via Agent Services Account, then linked to your HMRC Online Services account
- Self-assessment: via 64-8 or via Agent Services Account
- VAT (MTD): via Agent Services Account
- PAYE: via PAYE for Agents
- Construction Industry Scheme (CIS), if relevant
For Companies House filing, you need the company's Authentication code or to be added as a presenter. Plan two to three weeks lead time on agent authorisations: HMRC sometimes posts authentication codes to clients, which adds delay.
Setting up software
Standardise your software stack so onboarding is a checklist not an investigation:
- Cloud accounting: Xero, QuickBooks Online, Sage Business Cloud, FreeAgent
- Receipt capture: Dext, Hubdoc, AutoEntry
- Payroll: BrightPay, Moneysoft, IRIS Cascade, or your accounting software's payroll module
- Practice management: Senta, Karbon, Glide, Pixie, Bright Manager
- Engagement letter / e-signature: DocuSign, AdobeSign, or built-in to your practice management tool
- ID verification: SmartSearch, Veriphy, Credas
Automating onboarding via practice management software is a major time saver once you are doing more than two or three onboardings per month.
Kick-off and 30-day check-in
Within 30 days of go-live, schedule a follow-up to:
- Confirm software is working and bank feeds are reconciling
- Catch any missed information or misunderstandings
- Reset expectations on response times and process
- Identify any quick-win advisory issues (tax planning, structure, software setup)
The single highest-leverage move for a new practice is to write down the onboarding process as a checklist and run every client through it the same way. This is how you get from "every onboarding is different" to "we onboard a client in two weeks for a defined cost".
Common onboarding mistakes
- Starting work before AML is complete (risks both regulatory and recovery problems)
- Issuing an engagement letter that is generic and does not match the agreed services
- Forgetting to obtain agent authorisations early enough for the first deadline
- Not setting clear response-time expectations
- Not asking for predecessor handover, leading to information gaps mid-year
Key Takeaways
- Onboarding is a defined, repeatable process: discovery, proposal, AML, engagement letter, agent authorisations, software, kick-off
- AML is the highest-risk step: complete it thoroughly and use electronic ID verification
- Plan agent authorisations early: HMRC and Companies House both add lead time
- Standardise your software stack; automate via practice management software at scale
- A 30-day check-in catches issues early and sets the relationship's tone
Frequently asked questions
How long does onboarding take?
For a typical SME limited company, allow 5 to 10 working days from acceptance to fully operational, with most of the elapsed time waiting for HMRC agent authorisations and Companies House Authentication codes.
Can I start work before AML is complete?
Generally no. You should not provide regulated services until CDD is satisfied. Some firms allow limited preparatory work where the risk profile is low and CDD is in progress; take care and document the rationale.
Do I need to write to the predecessor accountant?
Yes. Professional clearance is a professional courtesy required by ICAEW, ACCA, AAT, ATT and CIOT, and the predecessor's response can flag professional reasons not to accept.
What software best automates onboarding?
Senta, Karbon, Glide, Pixie and Bright Manager all offer onboarding workflows, integrated with engagement letters and AML tools. The right choice depends on your firm size and stack.
Do I need a physical signature on the engagement letter?
No. E-signatures are valid in the UK under the Electronic Communications Act 2000 and Electronic Identification and Trust Services Regulations and are universally accepted in modern accountancy practice.