The Books Must Balance: Inside National Transit's Financial Statements

Why does a transport game need a balance sheet? Why does its income statement charge depreciation? And why did we spend weeks fixing a balance sheet that, as far as anyone could see, already balanced?

Most games keep the treasury as a single number. Build a road and it goes down; collect a toll and it goes up. That works fine until you try to ask it something. Am I actually making money, or just spending slowly? Is that expressway paying for itself, or quietly wearing out? A single number can’t answer that. A set of books can.

So National Transit keeps books. Open the Financial Report and you’ll find a balance sheet, an income statement, an annual report, a loan page and trend charts. Underneath all of them sits the equation from lesson one of any accounting course:

Assets = Liabilities + Equity

In plain terms: everything you have was either borrowed or is yours. In the game:

What you have: the money in your Transport Fund, plus what every road, railway, airport and waterway you’ve built is still worth.
What you borrowed: whatever you still owe on your loans.
What’s yours: the Capital Investment the nation put in at the start, plus the Retained Earnings your network has built up since.

The two sides have to be equal, and the interesting part is how they get there.

The plug

Plenty of people have kept a household budget. At the end of the month the numbers are $300 off, you can’t remember where it went, so you write in “Miscellaneous: $300” and call it done.

Accountants call that a “plug”. It’s the oldest trick there is, and the most dangerous: the books balance, but nobody will ever know where that $300 went. The mistake hasn’t been fixed. It’s been hidden.

National Transit’s balance sheet used to hide a plug of its own. Equity was calculated like this:

equity = total assets - total liabilities

See the problem? That balance sheet could never be out of balance, because equity was defined as “whatever makes it balance”. Whatever went wrong in the economy, that one line would soak it up without a trace, and the report would cheerfully tell you everything was fine.

So we deleted it. Now equity has to be worked out from its own records:

equity = capital investment + retained earnings

Cash and assets are counted on one side, loans on another, and what was invested and earned on a third. Three sets of records, kept separately, that have to agree at the end. If they don’t, something was recorded wrong, and now we can see it.

To make sure of that, we even wrote a test that feeds the report a deliberately wrong set of books (7 invested, 11 in cash) to check that the difference shows up. The comment on that test reads:

A deliberately inconsistent probe must expose, not conceal, the mismatch.

The bug it caught

The moment the plug was gone, a real problem surfaced: the game had been treating loan principal you paid back as money you’d spent.

Think about paying off a mortgage. Each payment is part interest and part principal. The interest is genuinely spent. The principal isn’t: pay back $10,000 and you owe the bank $10,000 less. Your net worth hasn’t moved.

The game had been booking both parts as expenses. So every repayment made the nation “lose” money that was never really lost, and the more you paid back, the poorer you looked. By rights the balance sheet should have stopped balancing long ago. It kept balancing because the plug had been covering for it all along.

Now, the only part of a loan that counts as an expense on the income statement is the interest. Principal Repayment is listed separately below Net Income: the money really does leave the fund, but it isn’t a loss.

Two bottom lines, never added together

Say you buy a car and plan to drive it for years. Every year it loses value, but you don’t pay anything for that. Then one year it needs a major overhaul, and you pay for it all at once.

If you recorded the loss in value every year and then also recorded the overhaul bill in the year it came due, you’d have counted the car’s wear twice.

Every road, railway, airport and waterway in the game works the same way, so each one reports two bottom lines: net profit, after depreciation, and net cash flow, after overhauls. The two are never added together, because they describe the same wear. The code says so bluntly: they are “deliberately NOT summable into one number.”

If a road’s cash flow looks great but it loses money once depreciation is counted, it’s going to send you a big bill one day. The gap between those two lines is the money you should be setting aside.

To stay with the car, here’s roughly how the game keeps the books on a road:

Buying a car isn’t this month’s spending; you now own something valuable. Building a road is the same: its cost goes on the books as an asset, so one big project doesn’t wreck the month.
A car loses a little value every month, so the game charges a little depreciation every month. Roads, airports and waterways are written off over 50 years, railways over 80. If construction costs in your country go up, depreciation goes up too, because the same road now costs more to rebuild.
After an overhaul the car is good for years more. So the money spent on an overhaul “buys back” part of the asset’s value and is added back to it, up to what it would cost to rebuild today. In the code’s words, “an overhaul buys the asset back at today’s prices.”
Once you’ve sold the car, it can’t stay on your books. Demolish a road, or upgrade an old one into a new one, and whatever value the old road had left is written off.

The act of Congress

Some early saves ran into trouble that wasn’t the player’s fault. The old borrowing limit was absurdly high: a young nation could borrow far more than it could ever pay back, and there was a “Maximum” button practically inviting you to press it. When we fixed the limit, those saves were left with debts they could never pay off.

The fix is a one-time act of Congress: when the save loads, the state steps in and settles that legacy debt once and for all.

So how should that money be recorded? The easy option is to book it as income. But then your nation would suddenly have one spectacular month where it made a fortune, a month that never really happened. If your family pays off your debts, that’s money from your family, not this month’s salary.

So it’s recorded as state capital, under Capital Investment on the balance sheet. The code comment says that putting it through the income statement “would fake a profitable month that never happened.” The same file also notes that this is fixing our own pricing mistake, not forgiving the player’s decisions.

Old saves, old books

Some older saves come from before these fixes, and their books may not quite agree when they load. We could have invented a bit of income or expense to close the gap, but that would just be a plug in nicer clothes.

What the game does instead: if last year’s books were wrong, correct last year’s books, and don’t charge it to this year. The difference is recorded as a correction to opening equity, known in accounting as a prior-period adjustment. It’s clearly marked as belonging to the past, so it can’t pass itself off as how your nation did this year.

Borrowing like a bank would lend

If you’ve ever applied for a mortgage, you know the bank looks at your income first: your monthly payments can’t be more than a certain share of it. National Transit sets your borrowing limit the same way. All your loan payments added together can’t exceed 80% of your average net operating cash flow over the last 12 months.

We’re careful about what counts as income here. Grants, tolls and taxes count, minus maintenance and operating costs. One-off income and spending don’t count. Neither do overhauls, because they’re keeping an asset alive, not day-to-day running costs.

If you really can’t make the next payment, you can restructure your debt: the loan’s term is stretched until the monthly payment fits back under that same 80% line. You still owe every cent. You just get more time to pay it back.

Why any of this matters in a game

You don’t need to know any accounting to play National Transit. You can build roads, watch cities grow, and never once open the Financial Report.

But if you do open it, the numbers are telling you the truth. A railway that looks profitable really is profitable, even after paying for its own wear. A loan that looks affordable really can be paid back. And the last line of the balance sheet, Liabilities + Equity, is shown in full, so you can check it against Total Assets yourself.