ERP data migration for small shops

Migrate master data and open balances. Leave closed history where it is. Old invoices, finished jobs and last year's purchase orders are useful for reference, but importing them costs weeks and brings past mistakes with them. Keep the old files read-only and export a few summary reports before switching off.

Items come first because everything else refers to them. Settle one code per physical part, one unit, one description style, and mark obsolete codes so they are left out. Then BOMs, as flat lines of parent, component, quantity, unit and scrap, using only the current revision. Then customers and vendors, deduped, with GSTIN or VAT number, currency and payment terms. Then open orders, as new documents. Each file should have one header row, no merged cells, no subtotals, and numbers stored as numbers.

Opening stock is the one record set that must not come from the old system. Pick a cut-over date, count the shelves that weekend, and load the count as opening movements per item and warehouse. The spreadsheet's running balance has drifted; loading it would make the ERP wrong from day one. Freeze receipts and issues in the old system from the count until go-live. Accounting opening balances follow at the next month end once operations are stable, so the accountant has a clean cut-off.

After import, check counts and samples rather than everything. The number of items, customers and vendors should match the cleaned file. Pick ten items at random and compare code, unit, description and stock to the count sheet. Open five BOMs and compare the lines. Then run three real orders end to end. Keep the import files with a date so the import can be repeated if a mistake is found, and record who signed off each record set. Only then switch off the old system.