Sequence matters more than speed
The failure mode in a platform move is almost never lost data. It is billing: a family charged twice, or a family charged by neither system because the cutover landed mid-cycle.
Avoid it by treating the invoice run as the cutover event rather than the import. Import everything, verify balances against the old statements, then let the old system finish its current cycle before you raise a single invoice in the new one.
Run both in parallel for that one cycle. It feels redundant and it is the step that turns a risky migration into an uneventful one.



