This wasn't built by a software company. It was built by someone who spends every working day inside institutional Excel systems that handle real money.
The idea came from a visit to a dentist. Young doctor, sharp, had just opened his own clinic — clean, modern, clearly good at the work. A proper bill was needed for an employer's reimbursement. He reached for a paper pad and wrote one out by hand, then mentioned he was trying to get some software built that could handle GST and keep his records straight.
The thought on the drive home was the same one you'd have about half the small businesses a bank officer sees: he doesn't need software. He needs the thing software does — minus the monthly bill, minus the cloud, minus the IT headache.
So it got built. In Excel. The same way the tools trusted with real money every day are built — precise, offline, and owned outright by the person using them.