There is no bad month to change accountants, but there are bad weeks. The three easiest moments are these.

• Just after your year end accounts and corporation tax return have been filed. The old firm has finished a complete cycle, the figures are settled, and the incoming firm starts from a clean opening position.
• Two to three months before your year end, so the new firm can look at your bookkeeping, your VAT position and how you pay yourself while there is still time to do something about it.
• When your current engagement letter comes up for renewal and the fee changes.

The week to avoid

Moving in the days before a filing or payment deadline creates risk for no reason. VAT returns and payments are normally due one calendar month and seven days after the period end. PAYE paid electronically is due by the 22nd of the month. If one of those falls inside your changeover window, let the current firm file it, then move.

If your accountant has gone quiet

Waiting is worse than moving when nobody is answering. Penalties for late filing accrue whether or not your accountant replies. If you have unfiled returns, say so at the first conversation, because that changes the order of work in the first month.

Pick your date first, then work backwards through the rest of the checklist.

Your own books and records are yours. That includes bank statements, sales invoices, purchase invoices and receipts, contracts, payroll records, and the data sitting inside your accounting software. An accountant holding those as your agent has to return them.

Working papers are different. The schedules and computations a firm prepares to get to the final figures generally belong to that firm. Most accountants pass over the useful ones anyway, because it makes the handover quicker for everyone. Some do not, and you have no right to insist.

Where fees are outstanding

If you owe your old accountant money, they may hold a lien over documents they own. They cannot hold documents belonging to you indefinitely, and they cannot block the handover as a negotiating tactic. Pay what is genuinely owed for work done, dispute what is not, and keep it in writing.

Do this before you give notice

• Export your accounting data and save a full backup somewhere you control, not in a shared drive the old firm administers.
• Check whose name the software subscription is in. If the licence belongs to the accountant, your access can disappear the day you leave.
• Download the last three years of filed accounts and tax returns, plus any HMRC correspondence you have.

We have rebuilt books for a retail client whose previous accountant, an unregulated sole practitioner, died and left no accessible records. We got copies of everything from HMRC, brought every return up to date and appealed the penalties, which were cancelled. It worked, and it took months. Saving your own copies first is cheaper than reconstruction.

Changing accountants does not change your HMRC record. What changes is who HMRC is allowed to talk to, and that is set up separately for each tax.

Your new accountant sends an authorisation request for each service you need: corporation tax, VAT, PAYE as an employer, Self Assessment, and Making Tax Digital for Income Tax where it applies. Some requests are approved online in minutes. Others still rely on a code posted to you, which adds time to the process. A new authorisation takes the place of the old agent’s, so there is no separate cancellation for you to chase.

What an agent can see

Authorisation is not cosmetic. For corporation tax, your agent gets access to company and financial information and can update the contact details HMRC holds. For PAYE as an employer, they can see your employees’ personal and financial details. The official position is set out in HMRC’s guidance on authorising an agent.

Two things that stay with you

You remain legally responsible for your own tax. When your accountant prepares a return, you check it and confirm the figures before it is submitted. That is the rule, and it is a good one, because the person who knows what the business actually did is you.

The second is your Companies House authentication code. It is posted to the registered office or an eligible home address, and you can request a fresh one if it has been lost with a previous adviser.

Give your new firm the go-ahead on the authorisation requests the day they arrive, because nothing else moves until they are in place.

Once you have signed an engagement letter with the new firm, most of the remaining work happens between the two accountants. You are copied in, and that is usually the extent of your involvement.

The incoming firm writes to your old accountant asking whether there is any reason it should not take the work on, and requesting the information needed to carry on properly. The outgoing firm replies and sends the handover pack. What should be in it:

• The last set of filed accounts and the corporation tax computation behind them.
• Capital allowances pools and any losses carried forward, with the figures that support them.
• Payroll records for the current tax year, including year to date figures for every employee.
• VAT returns filed and the records behind the last few periods.
• Access to, or a full backup of, the accounting software file.

If the reply does not come

Some firms answer in days. Some take weeks, and a handful never answer at all. A sensible new accountant does not sit and wait. They pull your filing history from Companies House, request your records from HMRC, and start the first month’s work from what is already available.

What you should ask about

The handover letter is a chance to tidy up loose ends. Ask whether any return is unfiled, whether any HMRC payment is outstanding, and whether anything was queried and left unresolved. Surprises are far cheaper to deal with in week one than in month six.

Tell your current accountant in a short email that you are moving. You do not owe anyone a reason.

Firms handle the cost of taking on a new client in different ways. Some absorb it. Some charge a separate onboarding fee that covers the acceptance checks, the clearance correspondence, setting up agent authorisation, importing your data, agreeing an opening position and mapping your deadlines for the year.

The amount depends on the state of the records. Clean books in cloud software are quick. Missing paperwork, historic errors or figures that have to be typed out of PDFs take real time, and any honest firm will tell you that before it starts rather than after.

What we do

We agree one fixed fee in writing before any work starts, and the handover carries no separate charge. We contact your current accountant for you, so you do not have to make that call. Calls, meetings and emails are never billed on top. If you want to move your bookkeeping to Xero, the migration is free, and we do your Companies House ID verification free as well. When that rule came in, plenty of firms were charging around fifty pounds a check.

Things nobody should be charging you for

• Releasing your own data from software you pay for.
• Removing an old agent from your HMRC record, which costs nothing and happens automatically when the new authorisation goes through.
• Anything described vaguely as a file release or exit administration charge with no itemised work behind it.

Ask for the fee and what it covers in writing, read it, and then sign.

The first month after a switch is where the money usually is, because it is the first time in years that somebody reads your history properly rather than rolling last year’s file forward.

A client came to us owing HMRC around twenty thousand pounds across corporation tax, VAT and Self Assessment, with no idea what any of it was for. We went through it line by line. A large part of the Self Assessment balance turned out to be payments on account built on estimates, so we filed his return early. That part of the debt was cancelled and HMRC wrote off the interest charged on it. He ended up knowing exactly what he owed and paying far less.

The things worth looking for

• Payments on account set too high because a return was estimated or filed late.
• Penalties with grounds for appeal that nobody appealed.
• Capital allowances and reliefs claimed in one year and quietly dropped the next.
• Welsh reliefs that only apply if you ask for them. We found ten thousand pounds of business rates relief for a Spar franchise owner in a first meeting, because he had carried on paying full rates from the Covid years and Cardiff Council only gave the relief to businesses that applied.

None of this is exotic. It is what a careful read of three years of filings turns up, and it is one of the better reasons to move while there is still time to act on what is found.