Started by just building better reports for pharmacies stuck on Marg ERP somehow I've now replaced it for 20 of them
This wasn't the plan. I never set out to "build an ERP."
It started because a couple of medical store / pharmacy clients were on Marg ERP and kept complaining about the same thing: the data was in there, but getting anything useful out of it was painful. So I started building intelligence reports for them, proper analytics on top of their existing Marg data. Fast-moving vs dead stock, margin leakage, expiry tracking, supplier-wise purchase patterns, the stuff that actually changes how a medical store buys and prices. GPT Like experience that let's them query their data
That part landed really well. Owners who'd been running on gut feel suddenly had numbers in front of them.
But then the requests kept creeping. "Can you also fix billing?" "Can it handle our GST returns?" "Why can't I just see this on my phone?" At some point I realized I was bolting more and more onto a system I didn't control, and it made more sense to just build the whole thing, our own ERP, with the reporting baked in from day one instead of duct-taped on top.
The first full replacement was genuinely nerve-wracking. Migrating live billing + inventory + tax data for a running medical store is not a "move fast and break things" situation. One bad migration and they can't bill customers tomorrow morning. We over-prepared, ran both systems in parallel for a bit, and it went fine.
Since then I've quietly done it for about 20 customers. Mostly word of mouth, one owner tells another.
Not posting this to pitch anything. Mostly curious if others here have gone down the "I built a feature on top of someone's software → ended up replacing the software" path, and how you handled the trust / data-migration side of it. That's the part that still makes me sweat every time.