Accepting an accountant’s quote does not make them your accountant. It starts a short onboarding sequence that does. Between “yes please” and the firm actually acting for you sit five stages: a contract to sign, legally required identity checks, your records and history changing hands, official authorisation with HMRC, and a proper setup conversation. Knowing the sequence in advance lets you move through it in days instead of weeks, because at almost every stage the thing being waited for is you.
Stage one: the engagement letter is the real agreement
The quote told you the price; the engagement letter is the contract. It defines the services included, the responsibilities on each side, how fees and extra work are handled, and how either party ends the arrangement. Read it properly, particularly the scope section, because “my accountant deals with that” disputes almost always trace back to a service that was never in scope. Anything you expected from the quote conversation that is missing from the letter should be raised before signing, while goodwill is at its peak and amendments cost nothing.
Stage two: identity checks are law, not suspicion
Accountancy firms are subject to anti-money-laundering regulations and must verify who their clients are before acting. Expect to provide photographic identity and proof of address, and for a company, details of directors and anyone with significant control. Some firms verify electronically, others want certified copies. None of this is negotiable and none of it is personal; a firm that skipped it would be the red flag. Supplying clean, current documents at the first request is the single easiest way to keep onboarding fast.
Stage three: your records and your history
The firm now needs the raw material: recent accounts and returns, your bookkeeping records in whatever form they exist, and the registrations, reference numbers and dates that define your tax position. If you are coming from another accountant, most of this arrives through the professional clearance and handover process described in how to switch accountants. If you are engaging an accountant for the first time, you are the source, which is why current GOV.UK guidance on record-keeping matters even before you have anyone to hand records to. Expect questions about the history; a firm that accepts your figures without any is doing you no favours.
Stage four: authority to act for you
For the firm to file returns and speak to HMRC on your behalf, agent authorisation must be established for each relevant tax. Depending on the tax and the route, this involves you approving a digital request or responding to codes sent to you. Until authorisation completes, the firm can prepare work but cannot deal with HMRC as your agent, so treat authorisation requests as same-day tasks, not paperwork for the weekend. If you use cloud accounting software, this stage also covers inviting the firm into your records at the right permission level, with the subscription staying in your name.
Stage five: the setup conversation that sets the tone
Good firms end onboarding with a structured conversation: your filing calendar for the year ahead and who owns each deadline, how and when you will exchange information, who your day-to-day contact is, and any immediate issues spotted in your prior-year figures. This is also your moment to state preferences: how often you want contact, what decisions you want flagged in advance, what worried you about the last arrangement. If you switched firms because of a problem, say so plainly; the new firm can only avoid repeating what it knows about. Owners who skipped this conversation are usually the ones reading when should a small business change accountants? two years later.
What you should see from the firm, and what they need from you
Through the whole sequence, a well-run firm gives you: a named contact, a checklist of exactly what they need, confirmation as each stage completes, and a clear statement of which upcoming deadlines they are taking responsibility for. What they need from you compresses to three behaviours: sign promptly, supply documents completely the first time, and answer queries within days. The elapsed time of onboarding, explored in how long does it take to change accountants?, is mostly the sum of these small turnarounds.
Frequently asked questions
Can I still back out after accepting a quote?
Before signing the engagement letter, freely. Afterwards, the letter’s termination terms apply, though a firm holds no power over you beyond fees for work actually done.
Why does my new accountant want my old returns?
Prior-year figures are the starting point for this year’s work, and reviewing them sometimes surfaces errors or unclaimed reliefs worth correcting. It is diligence, not nosiness.
What if I cannot find some of my records?
Tell the firm early rather than delaying. Much can be reconstructed from bank statements and HMRC’s own records once authorisation is in place, though reconstruction takes longer than retrieval.
When does the fee start being charged?
The engagement letter answers this, commonly from signature or from the start of the agreed service period. Onboarding itself is usually included in the quoted fee, but confirm rather than assume.
Does onboarding differ for a brand-new business?
The stages are the same minus the handover from a previous firm. First-time businesses spend the records stage on registrations and setup instead of history, which is often quicker.
See the sequence from our side
Every client we take on gets the checklist version of this process on day one, with named owners for each deadline. Our small business accountancy service page shows what the ongoing relationship includes. And if you are still at the comparing stage, request a quote and test how a firm behaves before you accept anything.