How to Migrate Your Whole Client Book From Xero to AccountsOS (2026 Practice Guide)

Moving an entire practice off Xero is a different problem from moving one company. You are not switching a single set of books. You are switching dozens, each with its own chart of accounts, open balances, VAT position and reconciliation state, and you need every one to land correctly without weeks of manual rekeying. This guide explains exactly how that works with AccountsOS, what data transfers, what you review, and what it costs against Xero's current per-client pricing.

The reader here is the practice owner or manager making the call, not the end client. Your clients will not need to log in or learn new software unless you want them to.

Why are practices moving their client book off Xero?

The trigger for most practices in 2026 is price, and specifically the way Xero's price has climbed while the bill has been broken into more pieces.

In September 2025 Xero raised its UK plan prices again. The Grow plan went from £33 to £37 a month, Comprehensive from £47 to £50, and Ultimate from £59 to £65. Layered on top of earlier rises, that is roughly a 23 percent cumulative increase inside a single year. For a practice running 40, 80 or 200 client files, a per-subscription rise of a few pounds is not a few pounds. It is a recurring annual cost increase across the entire book.

At the same time, features that used to sit inside a plan have been unbundled into separately metered add-ons. Payroll is charged at £1.50 per person, Expenses at £2.50 per user, Projects at £5 per user, and CIS at £5 a month. The cheapest entry plan, Ignite at £16, caps you at 20 invoices and 10 bills per month, which makes it unusable for most active trading clients, so in practice you are pushed up the tiers.

For a practice, the maths compounds. Every client on a mid or top tier, plus add-ons they actually use, plus the annual rise, is a cost base that grows whether or not your fees do. That is the pressure pushing practice owners to look at what else exists.

This is a software cost story, not a comment on the work. The migration question is simply whether the tool your clients sit on is still the right one for your margin.

What does migrating a whole client book actually involve?

Migrating one company is a known task. Migrating a book is the same task multiplied, and the risk is in the multiplication.

For each client you need to bring across:

• The trial balance, so the books open from the correct position.
• Contacts, meaning customers and suppliers, so invoicing and bills keep working.
• Open accounts receivable and accounts payable, the invoices and bills that are still outstanding on the day you switch.
• Opening balances for the bank and the ledger, posted as balanced double-entry.
• VAT history and the current VAT position, so returns continue without a gap.

Do that by hand for one client and it is a careful afternoon. Do it by hand for the whole book and it becomes a project measured in weeks, with a real chance of a transposed balance, a missed open invoice, or a VAT period that does not line up. The point of a proper migration tool is to remove the manual rekeying while keeping you in control of what posts.

The other half of the job is structural. Each client has to become its own isolated set of books, with its own chart of accounts and its own data, but all reachable from one place so you are not logging in and out of separate accounts all day.

How does AccountsOS migrate the client book?

AccountsOS treats the export, not the file name, as the source of truth. You paste or upload each client's Xero export, and the AI reads the actual content to work out what it is and what should be imported. It does not rely on a fixed template or a per-bank parser, so it copes with the variations you get across a real book.

For each client, the flow is the same:

1. AccountsOS creates a separate company for that client. Each client gets its own isolated books, chart of accounts and data.
2. The AI reads the export and identifies what it contains: trial balance, contacts, open invoices and bills, opening balances, VAT history.
3. It proposes how each item should be treated and maps it onto the AccountsOS chart of accounts.
4. It shows you a full preview of exactly what it will import, before anything is committed.
5. You review and approve. Only then does anything post to the books.

The division of labour matters here. The AI proposes the treatment, but the money side is not left to a language model. Deterministic code builds the double-entry and guarantees it balances, with any residual posted to an opening balances equity account rather than being fudged. The AI decides what something is. The accounting engine guarantees the numbers reconcile. You sign off before it is real.

Because the AI is doing the classification and mapping rather than a rigid importer, a messy or non-standard export does not stop the run. Anything it cannot resolve confidently is surfaced for your review instead of being silently dropped or forced into the wrong account.

How to migrate your client book, step by step

Here is the practical sequence for moving the whole book.

1. Set up your practice in AccountsOS. Create your practice account and open Practice Mode. This is the single dashboard you will run every client from.
2. Export each client from Xero. Pull the standard exports from Xero for each client: the trial balance, contacts, outstanding invoices and bills, and the VAT information. You are exporting your own clients' data, which you already have access to.
3. Import client by client. For each client, paste or upload the export into AccountsOS. It creates a company for that client and the AI reads the file.
4. Review the preview. AccountsOS shows you what it has identified and exactly what it will import for that client, including the trial balance, contacts, open AR and AP, opening balances and VAT history. Check it against what you know about the client.
5. Approve and post. Once you are happy, approve. The balanced double-entry posts to that client's books and the company is live.
6. Confirm the opening position and VAT. Verify the trial balance ties out and the VAT position is continuous, so the next return follows on cleanly.
7. Repeat across the book, then run from one dashboard. Work through your clients. From then on you operate every client from the single practice dashboard.

You control the pace. You can pilot with one or two clients to satisfy yourself the output is right, then move the rest once you trust the process.

What data comes across from Xero?

The migration is built to carry the things a practice cannot afford to lose.

Everything in that table is shown to you in the preview before it posts. The principle throughout is that the AI proposes and the deterministic engine executes balanced double-entry, and you are the final check.

What happens to your clients during the switch?

Nothing they have to act on. In Practice Mode, clients are covered by your practice plan and do not need their own login. The adviser has full access to every client's books from one dashboard.

That means the migration is something your practice does in the background. Clients do not get asked to set up an account, learn a new interface, or move their own data. If you later want to give a particular client access, you can, but it is not a requirement of the switch. For most practices that is the point: you change the tool you run the books on without putting any work onto the client.

How does Finn help you run more clients?

Once the book is migrated, the day to day changes because Finn, the AI accountant inside AccountsOS, does the repetitive work across every client.

Finn handles categorisation, reconciliation and month-end across the whole book. Rather than each person manually working through one client's bank feed at a time, Finn does the first pass and surfaces only the exceptions that need a human decision. The same applies to reconciliation and to closing each period.

The effect on a practice is leverage. When the routine categorise, reconcile and close cycle is largely automated and you only review what is genuinely uncertain, each member of the team can service more clients without the work expanding at the same rate. That is the operating case for the switch beyond the software bill: the cost base falls and the capacity per person rises.

AccountsOS is HMRC-recognised software for MTD VAT, so your VAT clients can file under Making Tax Digital. MTD for Income Tax is coming in April 2026, so plan around that timeline rather than treating it as already live.

What does AccountsOS Practice Mode cost compared with Xero?

This is where the per-client model and the practice model diverge sharply.

Xero is priced per client subscription. Each client file sits on a plan, and the plan price rose again in September 2025, with add-ons charged separately on top. Across a book, you are paying a subscription for every client plus whatever metered extras they use.

AccountsOS Practice Mode is one flat practice price. It is £299 a month for unlimited clients, or from £5 per client per month with a minimum of 20 clients. Clients are covered by the practice plan and are not billed their own subscription.

Run the comparison on your own numbers. A book of 40 clients on Xero mid tier is a recurring monthly cost in the four figures before add-ons. The same book under a flat practice plan does not scale with each new client in the same way. The more clients you run, the wider the gap.

Frequently Asked Questions

How long does it take to migrate a whole client book from Xero?

It depends on the size of the book, but the per-client work is fast because the AI reads each export and prepares the import for you to review, rather than you rekeying it. Most practices pilot with one or two clients to build confidence, then move the rest in batches. The bottleneck is your review and sign-off, not manual data entry.

Will anything post to the books before I have checked it?

No. For every client, AccountsOS shows you a full preview of exactly what it will import before anything is committed. The AI proposes the treatment, deterministic code builds the balanced double-entry, and you review and approve before it posts. Nothing hits a client's books without your sign-off.

Do my clients need to log in or do anything?

No. In Practice Mode, clients are covered by your practice plan and do not need their own login. The adviser has full access to every client from one dashboard. You can give a client access later if you choose, but it is not required to migrate or to run the books.

What data comes across from Xero?

The trial balance, contacts (customers and suppliers), open invoices and bills, opening balances, and VAT history. Each item is identified by the AI, mapped onto the AccountsOS chart of accounts, and shown to you in the preview before it posts. Money is handled by the accounting engine so the double-entry balances.

Is AccountsOS recognised by HMRC for MTD?

AccountsOS is HMRC-recognised software for MTD VAT, so your VAT clients can continue filing under Making Tax Digital after the switch. MTD for Income Tax is coming in April 2026, so factor that date into your planning rather than treating it as live today.

What does it cost to run a practice on AccountsOS?

Practice Mode is a single flat price: £299 a month for unlimited clients, or from £5 per client per month with a minimum of 20 clients. Clients are covered by your plan rather than each paying a separate subscription, which is the main cost difference against Xero's per-client model.

Can I migrate just some clients first to test it?

Yes. You can import one or two clients, review exactly what the AI prepared, confirm the trial balance and VAT position tie out, and only then move the rest of the book. There is no requirement to switch everyone at once.

Does the VAT position carry over so returns continue without a gap?

Yes. VAT history and the current VAT position are part of the migration, so the next return follows on from where the client was in Xero. As with everything else, the VAT data is shown in the preview for your review before it is committed.

Move your client book once, run it from one place

Migrating a practice off Xero is no longer a manual rekeying project. AccountsOS creates a company per client, the AI reads each export and prepares a reviewed import covering the trial balance, contacts, open invoices and bills, opening balances and VAT history, and nothing posts until you approve it. After that, Finn runs categorisation, reconciliation and month-end across the whole book, and one flat practice plan replaces a stack of per-client subscriptions.

See Practice Mode and migrate your client book at AccountsOS for accountants.