Changing Accountant: How to Switch Without Missing Deadlines

Can you change accountants at any time?

Yes. There is no notice period set in law, no HMRC approval process, and no restriction on the point in the tax year when you move.

Two things do apply. First, your engagement letter governs notice and any fees still owed, so read it before you write to your current firm. Second, and more importantly, the legal responsibility for filing returns and paying tax sits with you, not your accountant. HMRC states plainly that you remain responsible for your own tax and must check any return before your agent submits it. A handover does not pause a deadline or excuse a late payment.

How to switch accountants: the step-by-step process

1. Check your engagement letter. Look for the notice period, any disengagement fee, and how ongoing work in progress is billed.
2. Confirm the scope in writing with the new firm. Agree exactly which filings the incoming firm will handle and, critically, which return the outgoing firm will complete before it stops acting.
3. Tell your current accountant in writing. A short email is enough. Ask them to confirm the last piece of work they will complete.
4. The new firm sends a professional clearance letter. This asks the outgoing firm whether there is any professional reason the new firm should not accept the appointment, and requests handover information. It is a requirement of the accountancy professional bodies rather than a statutory rule.
5. Authorise the new firm with HMRC. The route depends on the tax (see below).
6. Transfer records and software access. Bookkeeping files, payroll data and Companies House details move across.
7. Remove the old authorisation. Do this once the new agent has confirmed access.

How HMRC agent authorisation actually works

HMRC does not use one authorisation method for everything. The route varies by tax service:

• Digital handshake: used for VAT, Making Tax Digital for Income Tax, Capital Gains Tax on UK Property, the Income Record Viewer, trusts and estates, Plastic Packaging Tax and Pillar 2. Your agent sends you a link, and you approve it through your Government Gateway account.
• Online Agent Authorisation or your business tax account: available for services including PAYE and Corporation Tax.
• Paper form 64-8: still required for some services, including individual PAYE and National Insurance.

Removing an agent works the same way in reverse, and the removal method depends on how the original authorisation was granted. If you want to change agents, HMRC confirms that submitting a new authorisation request replaces any existing authority for that service.

What documents do you need to switch accountants?

Prepare these three groups before the handover starts. Missing items are the most common cause of delay.

Identity and tax references

• Unique Taxpayer Reference (UTR)
• National Insurance number
• Company registration number
• VAT registration number
• PAYE reference and Accounts Office reference
• CIS contractor or subcontractor details, if relevant

Accounting records

• Last set of finalised accounts
• Most recent tax return and tax computation
• Trial balance and nominal ledger for the current period
• Fixed asset register with capital allowances history
• Bookkeeping software login or data file
• Bank statements covering the period since the last accounts
• Payroll records, including P11Ds and pension submissions

Company secretarial

• Companies House authentication code
• Confirmation statement review date
• Dividend vouchers and board minutes

The fixed asset register and capital allowances history are the items most often left behind, and they are the hardest to rebuild afterwards.

Which deadlines are at risk when you change accountant?

Making Tax Digital for Income Tax became mandatory on 6 April 2026 for sole traders and landlords whose qualifying income exceeded £50,000 on their 2024 to 2025 tax return. The threshold falls to over £30,000 from 6 April 2027, and down to £20,000 from 6 April 2028. Because each quarterly update reports cumulative figures from the start of the tax year, an incoming firm cannot simply pick up from the last three months. It needs the complete digital record for the year so far. Read our guide to [how Making Tax Digital for Income Tax quarterly updates work] if this applies to you.

When is the best time to switch accountants?

The cleanest window is shortly after a year end or immediately after a major filing is completed. The incoming firm starts from a finalised position rather than a part-finished one.

That said, waiting for a perfect moment while your current firm is already unresponsive usually costs more than moving now. Three periods need extra care: December and January, when self assessment tax return deadlines and corporation tax payment dates overlap; the four weeks before a company year end; and the run-up to a quarterly update date. Switching in these windows is possible, but agree in writing which firm files what before anyone disengages.

What if your current accountant will not release your records?

Your own books and records belong to you. The firm’s working papers, schedules and internal calculations belong to the firm, and it is not obliged to hand them over.

Where fees are outstanding, an accountant may exercise a lien over documents in its possession until payment is made. Practically, this means unpaid invoices are the most common reason a handover stalls. Settle any legitimate balance first. If the firm still fails to respond and it is regulated by a professional body such as the IFA, ICAEW, ACCA or AAT, that body operates a complaints process you can use.

Costs and common mistakes

Expect a possible disengagement or catch-up fee, and check whether you will briefly pay two firms at once if fee periods overlap.

Three mistakes cause most missed deadlines during a switch:

• Disengaging before the new authorisation is live. This leaves a window where no agent can file or speak to HMRC on your behalf.
• Assuming the old firm will complete one final return. Confirm this in writing or it will not happen.
• Leaving software subscriptions in the outgoing firm’s name. Xero and QuickBooks access can be withdrawn the day the relationship ends, taking your bookkeeping data with it.