From a
spreadsheet to
the App Store

Most budgeting apps connect to your bank, sort your spending for you and send your figures to their servers. Erkos does the opposite. You log every pound by hand, read each month as a statement, and your data stays on your iPhone and in your own iCloud.

It’s for people who already keep their money in a spreadsheet and want something calmer and more disciplined than a budgeting app. The idea underneath is a habit: log it every day, close the books every month, and every year see it add up.

The first version was a tool for one person: me. A Google Sheet held the ledger, and a phone web app read it as a dashboard and wrote entries back through the Sheets API, with a guard that refused to write if a row label didn’t match. It proved the ideas. Seeing each month as a statement changed how I spent, and logging by hand kept me honest.

Turning it into something others could pay for meant keeping those ideas and replacing everything that assumed me. The spreadsheet, my names and my own targets all had to go. Every name and figure in Erkos is now set by the person using it, and the record lives on their phone, not in a sheet.

The core of Erkos is a model, not a screen. Each month is laid out like a company’s cash flow statement: income, operating costs, cash from operations, financing, capital deployed and free cash flow. A surplus tops up your reserve; a shortfall comes out of it.

The language had to work for someone who has never read a set of accounts. Every term has one plain definition of 17 or 18 words, shared word for word by the in-app glossary and the website. Sections carry an ⓘ that explains what they show, and free cash flow’s works your own numbers through, so the statement teaches itself.

With no bank feed, logging has to be quick, but it shouldn’t be careless. The + sheet opens on the last category used, with the bank balance at the top. The button spells out exactly what it will do (“Hold to log £42.50”, then the category, month and direction) and fills over 0.9 seconds while held. Let go early and nothing is written.

Every entry ends in a receipt: amount, category, period, time and the new bank balance, with Undo one tap away. The wording was tuned in small rounds. “Hold to write · release to cancel” became just “Release to cancel”, and “hold to commit” became the feature’s name everywhere it’s explained.

The Flow tab opens on a flow of funds: a Sankey diagram drawn from scratch rather than taken from a charting library. Income enters on the left, splits into costs and cash from operations, then into free cash flow, capital deployed and financing on the right.

The web version had taught me what goes wrong. Labels landed on bands, so now each band runs level for a stretch either side of its node, leaving a clear space above for the label. A Sankey is a conservation diagram, so the layout is built to balance: when income falls short, the reserve or borrowing makes up the difference as its own outlined band.

Overview centres on a horizon dial: one tick per month across a plan of 5 to 25 years, on a 346° sweep with a gap at twelve o’clock. Each month you put money to work lights its tick orange. On launch the funded months sweep in, and a month that becomes funded pulses with a success haptic. With Reduce Motion on, the haptic stays and the movement goes.

The rest of the habit is built in too. An optional 9pm reminder rotates ten plain messages, never with figures or guilt. At the month’s end you close the books: a checklist, the statement against last month and a one-page PDF. The first time a month’s target is met, a short sheet says “Your future, funded”.

The private tool knew everything about me. Erkos knows nothing, so onboarding does the work: Welcome, How it works, then eight short steps (basics, income, spending, reserve, position, obligations, horizon and privacy) before a summary that ends in “Log my first entry”.

Each step ends with a short “What this is” card, so you learn the model while you set it up. Sensible defaults keep it quick: a starter set of categories in two groups, and a reserve target pre-filled at three months of running costs. A tour after setup points to each tab once.

“Your data never touches our servers” is the product’s promise, and it shaped every decision. There’s no backend, no account, no bank connection, and no analytics or crash-reporting SDK. Data lives in SwiftData on the phone and is set up to sync through the person’s own iCloud, with names, notes and figures marked for encryption. The App Store label will read Data Not Collected.

That rules out the usual product toolkit, so the design has to make up for it. Feedback comes by email and App Store reviews. A backup is a JSON file you save yourself, and the ledger exports as CSV. Privacy mode masks every figure and blurs the charts, with Face ID on top.

Erkos runs on a small design system of its own, carried over from the web version and rebuilt in SwiftUI. Every colour, typeface and component is defined once in code and shared by every screen and the Home Screen widget. The mockups on the site and in the App Store are drawn from parts that follow the same code, so they never drift from the app.

Erkos is published by its own company, Erkos Software Ltd. The site at erkos.app explains the idea and the terms, and hosts a Learn page, practical money guides, a press kit and support. Every app image used outside the app (the site, the App Store screenshots, social posts and a short promo video) is generated from one set of mockups whose parts follow the SwiftUI code, so marketing never drifts from the product.

Pricing was kept simple: a free month, then £29.99 a year or £79.99 for lifetime, with a launch price until the end of February 2027. There’s no free tier, no adverts and no data to sell.

The spreadsheet proved the idea worked for one person. Erkos is that idea rebuilt so anyone can use it, without anyone else ever seeing their figures.