The story

Your money is nobody’s business but yours.

I’m Kostas — a software engineer in Athens. I built BillPlex because every other money app I tried wanted something I wasn’t willing to give: my bank login, my data, or my attention.

It started with pen and paper

For years, we split our expenses the hard way — on paper. Who paid for what, who owed whom, scribbled on a notepad stuck to the fridge. Working out a fair split was a constant little argument.

And the big picture? We had no idea. No clue how much we really spent at the supermarket each month, or what a single holiday actually cost once everything was added up.

The apps that promised to fix this all wanted the same thing first: my bank login — access handed to a company I’d never heard of, so it could read every transaction I’d ever made.

But I’ve spent years building software for a living. I knew a money app didn’t have to work this way — that everything these apps did on a server could run privately, right on your phone. So I built the one I actually wanted, and I’ve been refining it ever since.

Tested in real life, every day

Me, long before BillPlex existed.
Me, long before BillPlex existed.

BillPlex isn’t tested only in a lab — it’s tested in daily use. Every release is lived in before it ships: real expenses, real splits, real households, including my own family’s. If something feels off in everyday use, it doesn’t go out.

My goal is straightforward: make BillPlex the best app in its category, with privacy at its core. I pour real effort into every detail — the interface, the polish, the way it feels in your hand — and the app is in full, active development, getting better with every release. Anything that confuses a real person is wrong, and it gets fixed before it reaches you.

What I’ll never do

  • Never ask for your bank login

    You type what you spend, or snap a photo of a receipt. That’s it.

  • Never upload your data by default

    Your expenses live on your phone. Syncing between your own devices is direct and encrypted — it never passes through me.

  • Never sell your data

    There’s nothing to sell, because I never collect it in the first place.

  • Never show you ads

    The app works for you, not for advertisers.

  • Never track you

    No analytics watching what you tap. No profile built behind your back.

So how do I keep the lights on?

How does a free app with no ads and no data harvesting survive? Honestly — and patiently.

Right now, BillPlex is completely free. It’s built to last and to be used for years — not to be flipped for a quick exit. Later, a few optional Pro features will help fund the work — but the core will always stay free.

What I will never do is make a cent from your data, your attention, or an ad. The day BillPlex charges for anything, you’ll be the customer — never the product.

— Kostas

Athens, Greece

Nexus Software Systems L.P.

Give it a try

No account. No bank login. Your data stays on your phone.

Download BillPlex