Replacing a legacy ERP: what moves, what gets rebuilt, and how to cut over

A legacy ERP is one that still works but no longer fits the business, whatever its age. The signs are familiar: a server one person logs into, customisations nobody documented, integrations that run on file drops, and a shrinking pool of people who can support it. Plenty of Australian factories and distributors run on systems like this. They are paid for and they run, but they get harder to staff, integrate and support each year. Our ERP migration service covers how we move businesses off them.

There's a newer cost too. If your ERP has no API and no export path, AI agents can't work against it. We won't build agents over a closed system like that, because there's nothing safe to connect them to.

Not every old system needs replacing. Stay where you are if the system is well configured, the team knows it, and the integrations around it would cost more to rebuild than the support contract. Other situations call for a different job:

• You're on an older Odoo version. That calls for an upgrade. Odoo's database upgrade service is free for Enterprise subscribers, and our Odoo upgrade services page covers what breaks and what it costs.
• You're mid-project and it's gone wrong. That's a rescue. A fixed-fee ERP implementation rescue assessment starts from A$1,200.
• You're on a subscription ERP and the renewal hurts. Plan the exit backwards from the renewal date. Our page on NetSuite alternatives in Australia covers when staying is the right call.

"The Exo sites that go live cleanly are the ones that decided early what they were not bringing. Every rehearsal we have seen run long was carrying history nobody had asked for. Load what you will act on, keep Exo readable for what you will only look up."

We implement both, so the choice follows fit. Odoo suits businesses that want one flexible platform across operations, with custom modules where the old system had bespoke code. MYOB Acumatica suits finance-led mid-market businesses that want multi-entity finance and Australian payroll in one cloud product.

Our Odoo vs MYOB Acumatica comparison covers the decision in more depth.

Master data and open items move. Closed history stays in the old system, and you report from it there.

• Chart of accounts and opening balances. The trial balance at cutover is loaded and reconciled. Prior periods go in as monthly net movements if you want comparatives, or stay in the old system if you don't.
• Customers, suppliers and items. Exported, cleaned and imported. Odoo imports CSV and Excel files for almost any record type, and MYOB Acumatica uses import scenarios.
• Open receivables and payables. Each open invoice and bill with its balance. MYOB Acumatica's migration mode loads them so they update customer and vendor balances without posting to the general ledger.
• Stock on hand. Quantities and costs by warehouse after a physical count, timed to the cutover.
• Open jobs, fixed assets and open orders. Loaded with cost to date, accumulated depreciation and open quantities.
• Rebuilt in the new system: bills of materials and routings (a migration is the one chance to correct years of BOM drift), custom code (re-specified against standard features first), reports, approval rules and integrations.

On history depth, two years of GL movements and twelve months of sales history is a common choice. Every extra year adds a reconciliation to every rehearsal. Rehearse the full load at least twice on a copy, reconcile each time, and only then load live.

Then keep the old system readable. The ATO requires most business records to be kept for 5 years and says you need to be able to reconstruct your original data if your record-keeping system changes. Don't switch the old server off on go-live day.

Go live at the start of a BAS quarter, so the last Business Activity Statement (BAS) comes from the closed old system and the first from the new one. Manufacturers phase it: finance, inventory and sales first, then production once stock accuracy is proven. Payroll cuts over at a pay-period start after a parallel run, and the ATO's guidance on changing payroll software sets out how year-to-date amounts and the new BMS ID are reported through Single Touch Payroll (STP). Payday Super has applied since 1 July 2026, so the last old-system pay run needs its super paid on time too.

From MYOB Exo, 12 to 20 weeks depending on whether job costing, CRM and payroll are in scope. A single-entity exit from a subscription ERP typically runs 3 to 5 months, planned backwards from the renewal date. Manufacturers usually take 3 to 6 months, phased.

On Odoo, our published Growth band is where Odoo starts replacing legacy ERP systems across departments: A$50,000 to A$120,000 ex GST for 15 to 50 users over 3 to 5 months. Enterprise scopes with multi-company, EDI or 3PL integrations start at A$120,000 and run 5 to 8 months, phased. MYOB Acumatica projects are scoped after discovery. If you want a costed roadmap before committing, Discovery and Scoping starts from A$5,000 ex GST and covers a gap analysis and a platform recommendation.

Josh Craig, a director of Auboros, has worked hands-on with more than 15 ERP platforms, including NetSuite, Dynamics, SAP, Oracle and Sage, and we've migrated businesses off NetSuite and Pronto. Our team has delivered more than 50 integrations, which matters when the old system has a decade of connections around it.