The job: your conversion date is a clean line — everything before it lives in the old system's archive, everything after it lives here, and the opening balances tie the two together to the cent.
1. Pick a conversion date. The start of a VAT period is the natural one (a month-end at minimum) — you never want a VAT return that straddles two systems. 2. Export three things from the old system: the chart of accounts, the customer & supplier list, and a trial balance as at your conversion date. Xero and Sage both export these as CSV; from a spreadsheet, shape the same three lists yourself. 3. Import them — Accounting → Import from Xero/Sage, in that order: - Chart of accounts — a CSV of code, name, type. Your account codes carry straight over, so old habits keep working. - Customers & suppliers — name and email; enough to invoice and capture bills on day one. - Opening trial balance — code, debit, credit. 360books checks it balances and posts a single, reversible opening journal at your conversion date. If the old TB was wrong, fix the journal — nothing else to unwind. 4. Bring the bank in line — import your first statement starting from the conversion date. The statement's opening balance should equal the bank figure in your opening TB; if it doesn't, that difference is usually uncleared payments — post them and move on. 5. Load the open items. Unpaid customer invoices and unpaid supplier bills at the conversion date get re-captured here (dated as issued) so reminders, age analysis and payment matching work — their total must equal the debtors and creditors lines in your opening TB. 6. Set the SARS profile — VAT category and number, PAYE if you run payroll — so the deadline calendar starts from your real obligations, not from zero. 7. Run one month in parallel. Keep the old system read-only, capture the first month here, and compare the month-end trial balances. When they agree, the old system becomes an archive and you stop paying for it.
Don't migrate old transaction history line by line — the opening TB carries the totals, and the old system's archive answers anything SARS asks about the years before. Details: Accounting & setup.