How do I switch accounting software in the middle of the year?

Short answer

Yes, with a clean cut off date, ideally the end of a VAT period or a month, from which the new ledger starts. Bring across opening balances, open invoices and bills, and your VAT settings. Keep the old system's records, because UK companies must keep them for 6 years.

When is the best moment to switch?

You can change software at any point in the year. The work is easier when the cut off date matches a period you already close. For most VAT registered businesses that is the end of a VAT quarter, because VAT Returns are usually due every 3 months and each 3 month span is an accounting period (GOV.UK). If you switch at the end of a quarter, the old system finishes one return and the new ledger starts the next.

The end of a month is the second best choice. A switch in the middle of a VAT quarter works too, but then the return for that quarter draws on two systems, and you have to make sure nothing is counted twice or left out.

What do I need to take across?

A mid year switch does not mean copying every past entry. You need the position on the cut off date and the items still open:

Opening balances. A trial balance from the old system on the cut off date: bank, cash, what customers owe, what you owe suppliers, VAT, loans, fixed assets and the profit so far this year.
Open invoices. Each unpaid sales invoice with its customer, date, number and amount, so payments can be matched later.
Open bills. Each unpaid supplier bill in the same way.
VAT settings. Your VAT number, the dates of your VAT periods and the scheme you use.
Master data. Customers, suppliers and your chart of accounts, if you want to keep the same structure.

Check that the opening trial balance in the new ledger agrees with the old one before you record anything new.

What happens to the records in the old system?

They stay your records. A company must keep its records for 6 years from the end of the last financial year they relate to, and longer in some cases, for example when a transaction covers more than one period (GOV.UK). VAT records must also be kept for at least 6 years (VAT Notice 700/21).

Before you cancel the old subscription, export the ledger, the reports, the VAT returns and the documents attached to entries, and store them where you can open them later. The same notice says data moving between programs for VAT must move through digital links, and copy and paste does not count as one. Keep that in mind if the quarter you switch in uses figures from both systems.

How does an AI ledger handle the switch?

An AI can do much of the routine work of a switch: read the old trial balance, record the opening balances as a journal entry, list the open invoices and bills, and check that the totals agree. It needs a proper ledger to write to.

Octobooks is one example. It is a double entry ledger for small companies and freelancers in the UK, Germany and Austria, run through your own AI, such as Claude. The connector has dozens of tools, including journal entries, the trial balance, upload of documents and bank statement files, and the VAT return workspace. You set the switches: for each company you choose who releases a booking. Every entry goes in through a release and stays in the audit trail.

This page is general information. It is not advice on your own case.

Sources

Updated 2026-10-20. General information, not tax advice for your own case.