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

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