The most common reason a migration stalls is a belief that the old books must be perfect before anything can move. They do not need to be perfect. They need to be explained.
What you are actually migrating
Two things: opening balances by account, and open items — the unpaid supplier invoices and uncollected customer invoices that make up your payables and receivables balances. Historical transaction detail is usually better left in the old system, archived and readable.
Attempting to bring ten years of line-level history across is where migrations lose months for very little benefit.
Reconcile once, properly
Pick a cutover date, ideally the start of a period. Produce a trial balance at that date and agree it. Then list open items and confirm that their totals equal the payables and receivables control balances. If they do not, the difference is a real problem in the old books and you have just found it — fix it before the import, not after.
Use the template
Opening balances and open items come in through an Excel import template. Prepare, review and import. Because the import is a file, it is reviewable before it posts and repeatable if something needs correcting.
Run a parallel close
Do one period in both systems. It feels wasteful and it is the single best predictor of a calm switchover. You are checking that the two closes agree, and more importantly that your team can produce the close in the new system without help.
A realistic sequence
- Agree the cutover date and freeze the chart of accounts.
- Reconcile the trial balance and open items at that date.
- Import opening balances, then open items.
- Verify control accounts tie back.
- Close one period in parallel.
- Switch, and keep the old system readable for reference.
Migration is mostly bookkeeping discipline, not technology. The import is the easy part.
