Migrating from Sage or A3 to Odoo: a guide to keeping your historical data

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Updated: 30 October 2026

To migrate from Sage or A3 to Odoo without losing your historical data, the usual approach is not to copy every entry from all previous financial years one by one. Instead, you choose a clean cut-off date (ideally the end of a quarter or of a financial year), load into Odoo the opening balances reconciled to the cent, the master data and the outstanding receivables and payables, and keep the old software in read-only mode for the legally required period. In the Basque Country there is one more piece to take care of: TicketBAI invoicing must have no gaps on the day of the switch.

In this guide we explain how we do it at Binovo, what is worth migrating and what is not, how long you must keep the accounting records from your previous software, and the mistakes we see most often in companies in Gipuzkoa, the Basque Country and Navarre.

Contents

Before you start: what changes when moving from Sage or A3 to Odoo

Sage (50, 200, ContaPlus) and A3 tend to focus on accounting and invoicing, and they often coexist with spreadsheets and standalone programs for warehouse management, purchasing or CRM. Odoo is a modular ERP: sales, purchasing, inventory, accounting, projects and manufacturing share the same database. That changes how you migrate: it is not just a matter of moving the accounting, but of deciding which processes move to Odoo and in what order.

In Spain, Odoo also has to speak the language of the tax authorities: the Spanish General Chart of Accounts (PGC), VAT returns, SII and, in the Basque Country, TicketBAI. At Binovo we work with the Spanish localization from the OCA community, which maintains these modules, and we are the authors of the OCA’s TicketBAI modules. If you want to see everything Odoo covers, we explain it on our Odoo ERP page.

How to choose the cut-off date

The cut-off date is the day from which everything is recorded in Odoo and the old software is no longer used for day-to-day operations.

  • The best option: 1 January. The whole financial year stays in a single program, it is closed in Sage or A3 as usual, and in Odoo you only need to load the opening entry.
  • Second option: the start of a quarter. The CopilotGestoria guide recommends the close of a calendar quarter, after filing Form 303 (and Form 130 or 131 if applicable), because the VAT already declared serves as a control figure. In Gipuzkoa, the equivalent reference is the quarterly foral self-assessments.
  • Mid-quarter: only if there is no alternative. No rule prohibits it, but it forces you to combine data from two programs for the same return and multiplies the chances of error.

If you switch mid-year, the legalization of the general journal has to cover the entire financial year, combining what was recorded in both programs, as CopilotGestoria points out.

What to migrate and what not to migrate

The temptation is to take everything with you. Experience shows it is better to migrate little but do it well, and leave the rest available for consultation in the old software.

Data Migrate? Comment
Chart of accounts Yes, adapted We start from the PGC in the Spanish localization and add the custom sub-accounts that are actually used.
Customers and suppliers Yes A good time to clean up duplicates, incorrect tax IDs and inactive records.
Products and price lists Yes Reviewing units of measure, taxes and the associated accounting accounts.
Opening balances Yes One opening entry at the cut-off date, reconciled with the balance sheet from the old software.
Outstanding receivables and payables (unpaid customer and supplier invoices) Yes, one by one This is what makes collections, payments, payment batches and aging reports work.
Unreconciled bank items Yes To get the bank accounts balanced from day one.
Journal entries from previous financial years Usually not Consulted in the old software. Ecosire suggests at most the last 12 months of the general ledger.
Historical bank reconciliations, attachments and links between documents No They are lost or must be documented separately; rebuilding them is not worth it.

Steps of an Odoo migration

  1. Analysis of the starting point. Which version of Sage or A3 is in use, which modules, how much data, which reports are essential and which integrations exist (banking, online store, tax advisor).
  2. Design of the processes in Odoo. The aim is not to copy how things were done in the old software, but to take advantage of what Odoo does out of the box.
  3. Chart of accounts and master data. Export, cleaning and loading of accounts, partners and products.
  4. Tax configuration. Taxes, fiscal positions, invoice series, TicketBAI or Verifactu, and SII if applicable.
  5. Test load. A full migration in a test environment, with a simulated close.
  6. Validation. Compare the trial balance, outstanding receivables and payables, and bank accounts between the two programs. Ecosire proposes a zero difference on balance sheet accounts as the criterion.
  7. Training and go-live. Final load at the cut-off date and support during the first weeks, especially for the first VAT close.

TicketBAI and SII on the day of the switch

What the official sources say, and our experience:

  • The new software must be registered. The TicketBAI service in Gipuzkoa is regulated by Foral Order 521/2020, and software is not certified: it is registered in the software register through a responsible declaration and receives a certificate number that goes inside every file, according to the frequently asked questions of the Provincial Tax Authority of Gipuzkoa (Hacienda Foral).
  • Each software, its own series. The same FAQ states that if several programs are used, invoices must carry a separate series for each one. In practice, when moving to Odoo we open new series and do not reuse those of the old software.
  • The chaining. Each TicketBAI file includes data from the previous invoice (series, number, date and part of its signature). That is why the last invoice from the old software must be closed and submitted before issuing the first one in Odoo, and the TicketBAI files issued up to that point must be kept.
  • SII. If your company is in the SII, the submission of records remains mandatory without interruption: everything issued or received before the cut-off must be sent from the old software, and everything after it from Odoo. It is advisable to review pending records before switching off the previous submission.

Outside the Basque Country, the reference will be Verifactu. The dates set by Royal Decree-law 15/2025 remain in force today, according to the Spanish Tax Agency: 1 January 2027 for Corporate Income Tax taxpayers and 1 July 2027 for everyone else. On 5 October 2026, the Ministry of Finance announced that it plans to postpone them until October 2028, in order to align them with mandatory electronic invoicing, but in its press release it presents this as a change that is still pending approval. We explain it in our article on the postponement of Verifactu to 2028. If you change software during this period, choose one that is already prepared, whatever the final date turns out to be. You can find more information at Verifactu in Odoo.

How long to keep the old software

Article 30 of the Commercial Code (consolidated text of the Official State Gazette, BOE) requires books, documentation and business supporting documents to be kept for six years from the last entry. The obligation lies with the business owner, not the software provider, and it does not disappear when you change software. On top of that come the tax deadlines: the CopilotGestoria guide recalls the general four-year limitation period of the General Tax Law and the ten-year period for auditing tax bases or amounts pending offset.

In practice we recommend:

  • Keeping a license or installation of the old software for read-only access, or at least a copy of the database that can be opened.
  • Exporting to PDF or Excel the general journal and ledger, the balance sheet, the VAT book and the returns filed for each financial year.
  • Keeping the TicketBAI files and the SII records issued with the previous software.

How long does it take to migrate to Odoo?

It depends on the size of the company, the processes that move to Odoo and the quality of the source data. As a reference, the Ecosire guide estimates 2 to 3 months to migrate from Sage 50 and 4 to 6 months from Sage 200, and includes a period of 30 to 60 days running both systems in parallel. These are Ecosire’s figures for its own method, not Binovo’s: every project is different, which is why we prefer to estimate after analyzing the specific case.

How we do it at Binovo and common mistakes

We have been working with Odoo since 2014 (and before that, OpenERP), and more than 100 companies have Odoo implemented or maintained by Binovo. In migrations from Sage or A3 we apply the same method as in any project: a functional consultant as your single point of contact, our in-house development team and deliveries in 15-day sprints, so the company sees and tests progress from the very beginning.

We implement stable versions of Odoo, not the latest one by default. Before taking a new version to customers, we stabilize it in Community and check that it has what they need: Spanish localization, TicketBAI, Verifactu and the OCA modules. In an accounting migration this matters more than any new feature: what counts is that the first VAT close goes well. We present both Odoo Community and Enterprise, and the customer decides.

The mistakes we see most often:

  • Migrating the entire history “just in case”. It slows the project down and adds nothing: that history is already in the old software.
  • Not reconciling the opening balances before going live. A small discrepancy on day one turns into hours of searching at the first close.
  • Loading outstanding receivables and payables as a single global balance. Afterwards, payments cannot be applied to each invoice.
  • Forgetting the tax advisor. If an external advisory firm (gestoría) files your taxes, it needs to take part in choosing the cut-off date and know how to obtain the data from Odoo.
  • Issuing the first invoice in Odoo while the last one from the old software is still pending submission to TicketBAI.

After go-live, Odoo maintenance and support ensures that the tax setup stays up to date with regulatory changes, because we apply the same patches to all our customers.

Frequently asked questions

Can you migrate from A3 to Odoo in the middle of the year?

Yes, no rule prevents it, but it is better to do it at the start of a financial year or a quarter, with the VAT for the previous period already filed.

Do all entries from previous years have to be moved to Odoo?

It is not necessary. The usual approach is to migrate opening balances, master data and outstanding receivables and payables, and consult the history in the old software.

How long must the accounting records from the old software be kept?

The Commercial Code requires six years from the last entry, and tax deadlines can extend this in some cases, such as tax bases pending offset.

What happens with TicketBAI if I change invoicing software?

The new program must be registered in the foral register, use its own invoice series and start up with the previous program’s invoicing closed and submitted.

How long does it take to migrate from Sage to Odoo?

It depends on the scope. Ecosire estimates 2 to 3 months from Sage 50 and 4 to 6 months from Sage 200; each project should be estimated after analyzing it.

Can I migrate to Odoo Community or does it have to be Enterprise?

Both editions work. With the OCA Spanish localization, Odoo Community covers Spanish accounting, TicketBAI and Verifactu.

Thinking of leaving Sage or A3?

If you are considering the switch, we can review your starting point with you, the cut-off date that suits you best, and which processes make sense to move to Odoo. Get in touch and we’ll go through it together.

Sources

Transparency: this article was produced with the help of artificial intelligence based on the sources cited, and was reviewed and validated by the Binovo team before publication.

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