A task-by-task guide for moving between accounting systems or ERPs — covering data migration, chart of accounts mapping, parallel run, and go-live cutover.
1. Pre-Migration Planning
- Business requirements documentedWhat the new system must do that the old one cannot — requirements signed off by finance lead and key stakeholders.
- System selection completedVendor chosen, contract signed, and implementation partner engaged with clear scope and deliverables.
- Project governance establishedNamed project owner, finance lead, IT lead, and executive sponsor; steering cadence agreed.
- Go-live date agreedIdeally at period-end (year-end or quarter-end) to minimise opening balance complexity and audit risk.
- Training plan confirmedAll finance users scheduled for training before go-live; training materials prepared and distributed.
- Data archiving policy confirmedOld system data retention period agreed — minimum 7 years for UK statutory purposes; storage solution identified.
2. Data Migration Preparation
- Chart of accounts mappedOld nominal codes mapped to new codes; one-to-one or consolidation decisions documented and approved.
- Opening balances extracted and agreedBalances as at migration date extracted from old system and agreed to signed-off trial balance.
- Master data cleanedDuplicate suppliers, customers, and nominal codes removed from old system before migration extract.
- Accounts payable extracted and validatedOpen invoices and unallocated payments extracted, validated, and agreed to aged creditor report.
- Accounts receivable extracted and validatedOutstanding invoices and credit notes extracted, validated, and agreed to aged debtor report.
- Fixed asset register exportedFull register exported with NBV, depreciation rates, asset classes, and acquisition dates for each asset.
- Bank transactions agreedOutstanding items at migration date listed and agreed; reconciling items documented before go-live.
3. Parallel Run
- Parallel run period agreedMinimum one month running both systems simultaneously; start and end dates confirmed with all users.
- Dual entry and output comparisonSame transactions entered in both systems; output compared at transaction level for discrepancies.
- Weekly reconciliation between systemsReconciliation between old and new system prepared and reviewed weekly throughout the parallel run.
- User acceptance testing completedKey reports from new system checked against old system output by named finance users; sign-off obtained.
- Sign-off criteria defined and metPass/fail criteria agreed before parallel run begins; all criteria met before proceeding to go-live.
4. Go-Live Cutover
- Old system lockedNo new transactions posted in old system after cutover date; all users notified and access restricted.
- Opening balances loaded and agreedOpening balances loaded into new system and agreed to the migration sign-off file before go-live.
- Bank feeds connected and testedBank feeds connected to new system; transactions pulling correctly and matching to statements.
- Access rights configuredAll active users have correct permissions; ex-employees and leavers removed; admin access restricted.
- Integrations testedPayroll, expenses, banking, and CRM connections verified and processing correctly in new system.
- Go-live communicatedNew system announced to wider business; process guides and support contacts distributed to all teams.
5. Post-Migration Validation
- First month-end close completedManagement accounts prepared in new system and compared to plan; any differences investigated.
- Audit trail confirmedAll migrated transactions retain original posting dates and values; no data has been altered in migration.
- Old system access restrictedOld system access reduced to read-only; decommission timeline agreed with IT and vendor.
- Lessons learned documentedPost-implementation review completed; findings documented and shared with project sponsor.
