I think both staff salaries and taxes would be great ideas to slow down the game economy.
Regarding taxes, I think think the following would need to be considered (if based on
Ireland).
VAT
VAT, as far as I can see, doesn't apply to airline tickets.
Corporation Tax
The corporation tax, charged on profits, is slightly more complex. It is 12.5% on the "trading income" and 25% on "non-trading income". From what I can see, the latter is concerned with income through means not related to the company's primary purpose, such as interest, foreign income or rental income (in properties one owns). There is more info
here, but I tend to think that all the profit sources in AM (tickets, in-flight food and aircraft rentals) would be classified as trading income - as these are the purposes of the company - i.e. that is what they have primarily set out to make money on.
So, the conclusion is that all the current profits should have 12.5% taken away.
Capital Gains/Losses
Capital gains are charged at 25%. It would be fairly simple to have an additional field for each aircraft (as these are the only transferable assets) which is "Last Sale Price", if a subsequent sale is greater than that amount, capital gains tax is charged on the difference (this would be relevant to people who buy planes and sell them new on the aircraft market).
Capital gains can be offset by capital losses - i.e. selling/scraping aircraft for less than they were purchased.
As far as I can see (
for example), capital losses can offset capital gains, but are not otherwise tax deductible, and further more can be used as tax deductions forever into the future.
I think the formula would be constructed thus:
Calculate net capital gain/loss on each sale
Add the losses/gains together (or... subtract losses from gains)
If there is a net capital loss, add it to the capital loss field (which would need to be added for each airline)
If there is a net capital gain, subtract it from the capital loss, until there are no capital loss credits left, and then charge 25% tax on the remainder.
I would note two things about capital gains/losses - firstly, almost every airline (except brokers, and perhaps some very successful unofficial brokers) would be operating at a net capital loss, and so, none of this would be relevant to them. Furthermore, I suspect capital gains would not be applied to brokers (or arguably unofficial ones), as that is their primary source of income (just like a shop buying goods cheaply and selling at a higher price), and as such profits through these means would be charged as corporation tax.
Perhaps this could be built into the role of broker - in that official brokers are unable to operate routes, but only pay a 12.5% corporation tax on capital gains, whereas other airlines (including unofficial brokers) would have to pay 25% capital gains (as they are supposed to be flying planes, and not dealing them).
Implementation in AM
Tax should be charged monthly (rather than yearly, as everything operates monthly in AM)
Lifetime capital losses field included with the airline's data
For regular airlines:
Corporation tax (12.5%) on all "profits" that are currently listed in the bank balance (tickets + misc income + rentals - rentals - maintenance - misc costs etc.)
Capital gains/losses tax on at 25%
For official brokers:
Net capital gains added to corporation tax
Corporation tax (12.5%) on profits (rentals - maintenance +/- capital gains)
I am not sure if aircraft purchases would count as tax deductions - as they are necessary expenditure to run the business... including them thus would ruin most of the use of the tax system, as AM airlines spend all their profits on planes while expanding - not resulting in any overall slowing of the economy.
That's all I can think of... you may want someone who knows more about tax to be sure, but I think that would be a workable (albeit fairly complex to implement) solution.