Checklist:
Migrating to Odoo in 30 days

Phase 2. Configuration (weeks 2-3)

Configuring Odoo is faster if you separate master data (products, customers, suppliers, chart of accounts) from processes (workflows, automations). Start with the master data because without it you can't test anything.

• Create the Odoo instance (odoo.sh recommended for 80% of cases)
• Set up the company, charts of accounts, Spanish taxation (PGC, VAT, withholdings)
• Activate modules according to phase 1 (not all at once — only the core ones first)
• Set up users and permission groups
• Customize views, fields and essential automations (Studio or Python)
• Set up emails (support@, info@ aliases, IMAP/SMTP connection)
• Set up payment gateways if you sell online (Redsys, Stripe, Bizum)
• Validate with the internal champion before moving on
• Activate VeriFactu (l10n_es_verifactu) and test invoice issuance

Phase 3. Data migration (week 3)

This is where most projects slip off schedule. The cause: underestimating the data quality of the old system. Set aside time to clean up.

• Export from your current system (Sage, Holded, A3, SAP B1, Gestión Click): customers, suppliers, products, pending journal entries
• Clean the data: duplicates, obsolete records, inconsistent fields
• Map old fields → Odoo fields (especially accounting accounts and categories)
• Load into an Odoo staging environment (NEVER directly into production)
• Validate balances point by point: the accounting balance matches between the old system and Odoo
• Validate customer and supplier balances (receivables/payables)
• Validate stock by warehouse and product
• Validate the history of open orders
• Decide the cut-off point (end of month / end of quarter / end of year)
• Full backup of the old system before the cut-off

Phase 4. Go-live and support (week 4+)

Go-live day is the most stressful. But if you've done phases 1-3 well, it should be a non-event. The first 4 weeks after go-live are critical for detecting and fixing issues.

• Final data load (with balances as of the cut-off date)
• Training for teams by department (hands-on sessions with real data)
• Documentation of key processes (screenshots + steps)
• Defined rollback plan (in case something critical fails in the first 48h)
• Communication to external customers and suppliers about the change (new portal URLs, new invoices)
• AEAT validation in the first month (VeriFactu submission, bank reconciliation, first VAT return)
• Review session at 2 weeks: what works, what doesn't, what to prioritize in future enhancements?
• Activate secondary modules (the nice-to-haves from phase 1) once operations are stable
• Define the monthly support cadence: hours, SLA, preferred channel
• Quarterly review with the internal champion to identify improvement opportunities

Common mistakes this guide saves you from

• Migrating everything at once — Better to start with accounting+invoicing and add the rest in waves.
• Not cleaning the data first — If your Sage has 8,000 customers with duplicates, Odoo will inherit them all.
• Skipping staging — Testing in production is costly; any error stays in the accounting books.
• Training at the end of the project — By the time they reach go-live, the team has already forgotten what they learned.
• Not defining an internal champion — Without someone to decide internally, the project gets stuck on sign-offs.
• Ignoring VeriFactu — Mandatory in 2026. Setting it up in phase 2 avoids last-minute rushes.
• Not measuring KPIs before and after — Without a baseline, you won't know if the migration improved anything.