Personal · Finance
A money system that works across two countries
Made-up numbers · real rules
ProductDataAI-assisted buildI'm American, living and paid in the UK. Two tax systems, two currencies and accounts that one country treats as tax-free and the other doesn't. Most money advice assumes you live in one country. So I built my own system: write the rules down once, then let software apply them every month.
- My numbers
- Rules
- Calculations
- Decision
Try it
Change the month and watch the rules react.
- Rent & bills £1,350
- Everyday £650
- Emergency fund £400
- Investing £350
- Not assigned £507
The rules, checking this month
- NoteBuilding the emergency fund to 6 months of essentials (£12,000).
- PassRoth IRA: grows tax-free in the US, and the UK–US tax treaty protects it in the UK.
- PassPension by salary sacrifice saves £81/month in tax and NI.
- Note£507 a month has no job yet. Give it one.
- PassEvery rule passes.
Take-home / month
£3,257
$4,234 · after tax, NI and pension
Emergency fund
3.5 months
of essentials · target 6, floor 3
Pension / month
£217
before tax, by salary sacrifice
After 5 years: emergency fund £12,000, investments £44,765.
Decision
On track. Emergency fund full in 13 months, then savings switch to investing.
Made-up demo values. Simplified UK income tax and NI (England, 2026/27; no student loan). 5% yearly growth is an assumption, not a forecast. Not financial advice.
How I built it
- 1
Define the problem
Two countries' tax rules, one salary. Advice written for one country breaks.
- 2
Think through the solution
Write the rules down once, so money decisions stop depending on memory.
- 3
Apply AI
Use AI as a coding partner to turn those rules into working software.
- 4
Set up the system
Dashboards on laptop, tablet and phone that update themselves.