Clean the data before you migrate it

So the decision's made. You're changing systems. Good. Let's make sure it works.

There's one window in every migration that never comes back. It's the stretch before cutover, when the old system is still running and the new one hasn't earned anyone's trust yet. Both systems are alive at the same time. It's the only moment you can hold one up against the other and check.

Turn the old system off, and every question about a number becomes an investigation.

So don't waste the window. Here's what to prove before go-live.

Your old system is the answer key

I know. It's the system you're paying to get rid of. But it holds years of results your leadership, your auditors, and your lenders have already accepted. That makes it the most valuable reference you have.

Here's the standard for a clean migration:

Same answers where the old system was right. Better answers where it wasn't. And a written reason for every difference.

Not "it looks right." Not "the totals match." Every difference is either a mistake you fix or a change you made on purpose and documented. There's no third category.

And you can only prove it while both systems exist.

Four things to prove before go-live

Tie the opening balances, line by line. A trial balance that ties in total can be wrong on every single line. Tie it by account and by entity, to the cent. Find the differences now, not in the middle of your first close.

Turn every correction into a rule. Every manual fix your team makes today needs a home in the new world: a mapping, a configured rule, a governed layer around the system. No home means it comes back as a manual fix. Except now nobody remembers why it exists. Give every correction a written rule and an owner before cutover.

Clean the master data. Duplicate customers. Vendors nobody's paid in three years. Accounts nobody can explain. They don't get better in a new system. They get converted, and then they're harder to remove. Merge them, retire them, or remap them before the data moves.

Run a parallel close. Close the same period in both systems and reconcile them. Every difference gets fixed or documented. The old system stays on until every difference has an answer. Not one day sooner.

Don't settle for the flat file

Here's what usually happens to your history. The vendor converts a slice of it, then hands you the rest as a flat file export. A giant table in a folder. Technically, your history is preserved. Practically, it's gone.

Try running a trend on it. Try comparing this quarter to the same quarter three years ago when half your accounts were renamed in the migration. Try answering an auditor's question from a flat file with the old chart of accounts. You can't, not without someone rebuilding the logic by hand every time.

There's a better way, and it's a win on both sides.

Before you turn the old system off, pull final static data dumps: the closed periods, at the detail you'll actually need. Then build a reporting model, in Power BI or whatever your team uses, that maps that history into the new structure. Old accounts translate to new accounts. Old entities line up with new entities. The crosswalk lives inside the model as a governed rule, not in someone's spreadsheet.

Now your history and your new system speak the same language.

You keep your trending. Year-over-year still works on day one. Your comparatives don't break in the first board deck after go-live. And every historical number still ties back to the old system's final trial balance, so you can prove it's right.

You didn't just preserve your history. You harmonized it. That's the difference between an archive and an asset.

Readiness is finance's call

The implementation team will tell you the system is configured. That's their deliverable, and it's a real one. But configured isn't the same as ready. Whether the numbers are ready is your call, and it should stay yours.

Put a name next to each of the four checks. Write down what "done" means. Do it before the timeline gets tight, because when the timeline gets tight, the checks are what get squeezed.

The rule is the same one I use for every report. If it doesn't tie, it doesn't ship. That goes for a go-live date too.

Here's the payoff

Get these right and your new system starts life with balances everyone trusts, rules your team owns, and a history that still answers questions.

Your first close on the new system stops being a recovery. It becomes a confirmation.

That's the migration you were promised. You just have to prove it before you flip the switch.

If your cutover is on the calendar and these checks aren't, let's look at where your data stands before it moves. That's what a Systems Diagnostic is for. Start with a free 30-minute call.