A player wrote to tell us they had lost a cafe in Preston to a bill nobody warned them about. They traded well through a modelled 2019, crossed the VAT registration threshold in the October, kept their prices exactly where they were, and found in February that a sixth of everything they had taken since December had never been theirs.
They thought it was a bug. It was the game working.
A threshold makes a decision, a slider makes a shrug
Most management games treat tax as a percentage taken off the bottom line. Sometimes it is a difficulty setting. Occasionally it is a number in a city policy screen you can nudge. In every case it is the same thing: a multiplier applied at the end of the month to a figure you have already earned.
A multiplier cannot be played against. There is no move that answers it. You can earn more, which you were trying to do anyway, and that is the end of the interaction.
A threshold is different, because a threshold has a near side and a far side and a moment where you are standing on it. The VAT registration threshold has been £90,000 since 1 April 2024 and it is tested on a rolling twelve months, so the question arrives in the middle of a good autumn rather than at a year end. Take the December work and you are registered from February. Turn it down and you are a business that has chosen to stop growing. Take it and put your prices up first and you are a business that has planned.
Those are three different moves. That is a decision.
Britain is unusually full of them, which is a large part of why we set the game here. Before 4 December 2014 stamp duty was a slab tax, so a house at £250,000 paid £2,500 and a house at £250,001 paid three times that. The personal allowance is withdrawn by £1 for every £2 of income above £100,000, which creates a band where an extra pound of salary is taxed at an effective 60% and then stops being. Small business rate relief in England gives full relief up to a rateable value of £12,000 and tapers away by £15,000, so a slightly better unit can cost you more than the rent difference.
None of these are interesting as arithmetic. All of them are interesting as positions on a board.
The rules are the map, not the weather
We carry headline UK tax rules by year from 1930/31 onward, and the reason is not completeness. It is that the rules are what makes one decade feel unlike another when you are sitting inside it.
VAT does not exist in the game before April 1973, because it did not exist. A firm starting in 1972 keeps records for a tax on its profits and nothing else, and then a tax on its sales arrives and changes what being in business involves. A firm starting in 1988 borrows into a market where credit has just become easy and security is a house that is going up. A firm starting in 2009 has an overdraft that can be reviewed.
We never write a paragraph telling you the 1970s were inflationary. We let you quote a job in March and buy the materials in June.
We simplify the arithmetic and never the shape
There is a line, and it is worth being honest about where it sits.
We simplify calculation. We do not model every partial exemption method, every capital allowance pool and every anti-avoidance provision that has ever applied to a company of eleven people. We take headline rates, main reliefs, the ones a real small firm would actually meet, and we compute them to the penny in integer arithmetic so the result is the same on every machine.
We do not simplify structure. The dates stay where they are. The thresholds stay cliffs rather than being smoothed into gradients, because smoothing them would delete the decision and leave the number. The payment deadlines keep their real spacing, which is why the VAT quarter and the Corporation Tax payment can land in the same eight weeks and the fact that you were profitable all year turns out not to help.
If a rule is complicated in a way that produces no choice, we approximate it. If a rule is complicated in a way that produces a choice, it stays complicated.
The line is drawn where advice would start
The game models British tax. It does not give you advice about yours.
That distinction matters more than it sounds. A simulation can be right in shape and still be wrong for your particular circumstances, because your circumstances involve a spouse, a pension, a property, a previous year and a hundred other things the model has never heard of. We have seen people use the VAT threshold screen to think about their own business and we think that is a reasonable thing to do, in the way that a map is reasonable for thinking about a walk. It is not a substitute for somebody who has read your books.
So the rules in the game are dated and documented, the calculations are visible, and when a figure looks wrong you can open the working. What we will not do is put a disclaimer on a loading screen and then quietly round the rules off so the game is easier to balance.
Why we care about this
We build simulations of running a business in Britain, and in Britain the rules are most of what running a business feels like. Take them out and you have a spreadsheet with a graph on it. Leave them in, dated to the month across 1930 to 2040, and the cafe in Preston is a real problem with three real answers, only one of which you thought of in October. That is the game we wanted to play, so it is the one we built.