A real budget and tax model, not a prompt
Every figure traces back to a rule or a live balance. The assistant explains the numbers - it never invents them, and it can’t talk you past the maths.
About
The maths comes first. The AI just explains it.
Surplus is a savings copilot with a real budget and UK tax engine underneath - built by a chartered accountant who got tired of apps that show you a balance and call it budgeting.
Who’s building it
Seven years of getting other people’s numbers right, pointed at yours.
- 2022 Chartered accountant, qualified with ICAS
- 3 yrs At EY, in practice
- 3 yrs Finance and strategy at Squares, a UK payments fintech
- MEng Engineering, before the accountancy
The honest version
I built it because I was off-track myself.
I’m a chartered accountant who was quietly missing my own savings goal. Not because I couldn’t do the maths - because no app would do it for me.
I trained at EY and qualified with ICAS in 2022, then spent four years in finance and strategy, three of them at Squares, a UK payments fintech. You learn quickly that the useful work happens in the engine and not the interface. Before accountancy I did a masters in engineering, which is probably why my instinct was to build the model rather than nag myself harder.
An app that shows you your balance hasn’t done any of the work.
So I built the tool I wanted: a copilot that understands PAYE, National Insurance, student loan thresholds and salary sacrifice, tells you what’s genuinely safe to spend and paces you to the goal that matters. It acts first, shows its working and then checks what actually happened.
It’s still me building it, which is rather the point - the person answering your email is the person who wrote the tax logic.
Why it’s built differently
An engine with a copilot on top, not a chatbot with a balance.
Surplus models your month - tax, bills, pace, goals - and only then lets the assistant open its mouth.
UK depth, by design
The bits other apps round away are modelled properly.
- PAYE
- National Insurance
- Student loan plans
- Salary sacrifice
- Pension relief
Safe to spend, actually calculated
Committed bills, tax and the pace to your goal come out first. What’s left is a number you can spend without checking twice.
Read-only, always
Bank connections run through Yapily as an FCA-regulated account information service. Surplus can see your balances. It has no payment rail at all.