Budget

The city budget constitutes the amount of cash you, as mayor, have available for building and maintaining services and city infrastructure.

Uses

There are two distinct uses for your budget:

Construction

Everything you build will cost money, even setting zones for indsutries or residencies. Some big projects like Airports or Harbors cost millions.

Maintenance

After you build anything in your city, which is not a private-run business, you need to pay for its maintenance. This includes city infrastructure, like roads or rails, or the utilities buildings, and all the state-run activities and services in your city, such as education, health services, or leisure facilities. The amount of money needed is deducted from your budget each tick, and you can't control that amount (short of destroying a building).

Budget composition

The city Budget, just as other budgets, has two sections: Income and Expenses. The above two items (Construction and Maintenance) constitute the major part of your Expenses, along with any imports you need to pay cash for. And here is what constitutes your income:

Taxes: All private businesses, such as Industries, Hotels or Retail shops, have to pay for the right to conduct business in your city. Citizens also pay for the right to live in and use the services of the city.
Exports: sell your excess resource production to other cities or Omnicorp to earn cash.

All income increases your budget every tick (month), just as the maintenance fees decrease it. The term cashflow is used to determine the difference per tick between money entering and leaving the Budget. Its number is right next to the main Budget number, and shows graphically (with an arrow) if you gain or lose money.

The Budget panel

This panel gives youdetailed information about your city's financial situation, and allows you to control it. There are several subtabs in the panel:

General: Provides an overview of your city budget, divided by income and expenses. You can see how much does each category (such as Security, or Environment) contribute or cost to the city currently.
Taxes: Here you can set the tax policy for each of the taxable entities in the city: the four citizen classes and all types of private business. The minimum amount of taxes is 10%, maximum - 30%. By default Citizens start with 15%, while businesses - 25%. A taxes satisfaction indicator is also present.
Expenses: Here you get detailed information of all categories of buildings or infrastructures, maintained by the city.
Most profitable: The individual buildings that pay most taxes, in descending order
Most expensive: The individual buildings that cost most to maintain.
Loans: Here you can contract a loan. There are three amounts possible: 100,000 c, 500,000 c and 1,000,000 c. All of them must be repayed in 50 installments. Note that the repayment of a loan adds to the Expenses part of the budget for the next 50 months (the quantities are respectively 2000, 10,000 and 20,000 c/mo), so be very careful when you take a loan! Only use if you definitely want this extra amount of cash for some immediate purpose.

Considerations

As a successful and responsible mayor, your job is to make sure your income is always greater than your expenses. This will ensure the steady growth of the budget and your ability to continue expanding the city and eventually meet any hardships that circumstances impose on you.

Fortunately, CXL is a game that, once figured out, doesn't pose serious problems in that direction. You have to be really irresponsible not to manage to maintain a positive cashflow. Also, there are very few random factors occurring in the game (for now), such as the sudden bankruptcy of companies without any real reason (other than "The boss went out for a coffee break and never came back"), or citizens deciding to change their transport mode. For the rest, the economic situation stays stable once you bring it into balance. So, once you keep in mind:

How much will each new building or infrastructure cost you
How can you quickly ensure more tax income, and
How and what can you quickly sell to Omnicorp

... you shouldn't have any problems with maintaining a healthy positive cashflow.