Changing accounting system – how to avoid losing data

The risk is not the move itself, but the old system being closed before the history is secured. Reconcile up to the cut-off date, extract the general ledger, the subledgers, the document archive and SAF-T, check the opening balances reconcile back to the old system, and test e-invoicing, the bank and Altinn access before the subscription ends. From 1 January 2027 SAF-T 1.40 is the only valid format for new periods.

Three parts, in this order

A good system change is secure the history → reconcile the transition → test the new solution. The biggest risk is not the migration. It arises when the old subscription is cancelled before the business has secured the accounting data, the records, the open items, the payroll history and the documentation it still has to retain. After notice is given, some suppliers restrict access or export options. The order is therefore not a recommendation – it is the whole point.

When should you change?

There is no statutory date. 1 January is often simplest, because a new financial year starts and the profit and loss accounts start at nil. It can then be enough to establish the opening balance, the open customer and supplier items and the necessary history in the new system. But you can change mid-year. That can be practical once a month or a VAT period has been booked and reconciled. What matters is defining a clear cut-off date and deciding which system is the main system for which period.

Two ways to change mid-year

If you change on 1 July, the migration can broadly be done two ways. Move balances and open items. The old system keeps the detail for January to June. The new one starts with reconciled balances and open items at the cut-off date. The history then has to be kept separately so earlier transactions can still be verified. Move the whole year's transactions. Import everything from 1 January. That gives one complete financial year in the new solution, but requires more migration and more checking. Which is better depends on the systems, the volume of data and how good the new system's import options are.

What should be extracted before closure?

It will often be sensible to secure the general ledger and bookkeeping specification, the trial balance, the customer and supplier ledgers with open items, records, invoices and receipts, bank reconciliations, VAT specifications and earlier filings, the fixed asset register, the relevant payroll history, the annual accounts and tax returns, agreements – and a SAF-T file for the relevant periods. The law does not require exactly that package in every business. The point is simpler: the old system must not be closed before the business has secured all accounting records it still has to retain. The deadlines are in Retention of accounting records

SAF-T is useful – but it is not the whole of the accounts

SAF-T is a standardised format for recorded accounting data. It makes it easier to give Skatteetaten data on an audit, share data with an auditor or accountant, analyse accounting data and move data between systems. But a SAF-T file is not a backup. It contains recorded information and specifications. It does not necessarily contain the PDF invoices, the receipt images, the contracts or the stock count lists you need to document the transactions. So secure both SAF-T and the document archive. That is the one mistake most expensive to discover afterwards, because the documentation then often exists nowhere.

A new SAF-T standard from 2027

This matters particularly for a system change happening now. Skatteetaten published SAF-T Financial 1.40 on 31 August 2026. It can be adopted immediately and is fully backwards compatible. From 1 January 2027, 1.40 becomes the only valid SAF-T format. Version 1.30 can be used until 31 December 2026, and older versions apply to earlier financial years. If you are choosing a new system now, check that the supplier supports SAF-T 1.40 – not merely that it supports SAF-T.

Reconcile before you move, not after

A good system change starts with tidy old accounts. Before the cut-off date the bank, the customer and supplier ledgers, VAT and the relevant balance sheet accounts should be reconciled. Where the old system already contains differences, it becomes far harder to know whether a discrepancy in the new one comes from the migration or from an old error. A system change cannot be used to reset problems. Find and document them first.

The opening balance has to be traceable

The balances transferred have to reconcile back to the old accounts. That does not mean account 1230 has to become account 1230. The new system can have a different chart of accounts. But the totals have to be followable through a documented mapping. The same applies to open items: the total of the imported trade receivables has to match the total in the general ledger, and likewise for trade payables. Produce a separate migration reconciliation showing old balance → new account → imported balance → any documented difference. You then have an audit trail when the question arises in two years. Why the audit trail has to run both ways is in Digital document flow

Employers: the year-to-date figures are the critical part

Older guides on system changes refer to reconciling a separate tax withholding account. That is no longer the arrangement. From 1 January 2026 the withholding account requirement was removed. The advance deduction now goes directly to Skatteetaten by the first working day after the salary is paid. On changing payroll or accounting system, employers should check that employees and pay types have transferred correctly, and that the holiday pay basis, the year-to-date figures, benefits in kind, employer's contributions, the advance deduction, the payment routine towards Skatteetaten and the a-melding reporting are all correct. An error in the year-to-date figures affects the rest of the payroll year and is usually only discovered at the year end – see A monthly checklist for the payroll run

Invoice numbers have to stay verifiable

Section 5-1-3 of the Bookkeeping Regulations requires sales documents to be pre-numbered on printed forms or to have machine-assigned numbers in a verifiable sequence, or other marking making it easy to check that every sale has been registered. The new system does not have to continue with the next number from the old one. You can use a clearly new number series, as long as it remains easy to see which series belongs to which system and that the registration is complete. What you have to avoid is duplicates and unexplained gaps.

E-invoicing, the bank and Altinn have to be tested separately

E-invoicing. Invoices have to arrive in the new solution from the right date. Norwegian e-invoices travel through the Peppol infrastructure, and the recipient's access point is registered in ELMA. It is the access point provider that registers the recipient there. Coordinate the timing with suppliers, and send a test invoice before the old channel closes. The bank. A new system usually means a new bank connection. Check which accounts are to be linked, who can register and who approves payments, the payment reference set-up, the bank agreements and the payment files or API integrations. Test both incoming and outgoing payments. Altinn. Altinn's technical access management has changed. System access is used to let an accounting, payroll or HR system retrieve and send information on the business's behalf, such as the a-melding or the VAT return. Check that the new system has the necessary system access, that any accountant has the right authorisations, and that the reporting actually goes through from the new solution. None of those three follows automatically. Assume each has to be set up afresh.

A checklist before the old system closes

The accounts up to the cut-off date are booked and reconciled · the general ledger and trial balance are secured · the subledgers with open items are exported · records and documentation are downloaded or migrated · the payroll history and holiday pay basis are secured · SAF-T is exported for the relevant periods · the opening balances in the new system are checked · e-invoice receipt is tested · the bank integration works · the invoice numbering is checked · system access works from the new system · you know where the historical data will be kept afterwards. Do you have to keep paying for the old system for five years? Not necessarily. The retention obligation does not require the old solution to stay active, provided the necessary recorded information, records and other documentation have been exported and are kept as the bookkeeping rules require. In some cases read-only access can still be simpler or cheaper – but that has to be settled before notice is given.

Changing system and accountant at the same time?

Then plan the transitions together. There is little to gain from the old accountant moving everything into a new system the day before a new accountant takes over and wants a different one. Settle first which system will be used, who carries out the migration, the date the old bookkeeping stops, the date the new bookkeeping starts, and who checks the opening balance and the open items. The change of accountant itself is described in Switching accountant, and the systems we work with are on Accounting systems. Greenleaf can help with the set-up, the transfer and the checking so the continuing bookkeeping and reporting carry on without a break.

This is general guidance, not advice on your specific case. Deadlines, rates and amounts change – always check the current rules, or get in touch with us.

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We can work out what actually has to be done, what documentation exists and how quickly it can be sorted. You can also reach us in the evenings and at weekends.

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