Early in the game it is easy to tell how you are doing based on the red or green number in the top right of the screen. This shows whether you are gaining or losing money, and as long as you keep it green, you are doing good. This can get more difficult as you start trading however, as the import taxes hit all at once, and can turn that green number red for a single day. Depending on what management on the receiving side, this number can swing wildly the other way as well. The only way to know if you actually made a profit is to check the finance screen which will give you an overview of everything that has happened that month.

Every time there is a transaction, it gets logged into the finances table.

Most of it is pretty self-explanatory, but I will go over what it all means.

PROFITS

Raw Materials - Mined Items

Crops - Farmed Items

Animal Products - Items that are generated by farming animals.

Food - Products that can be eaten (non-crops)

Refined Materials - Anything that has passed through a refinery

Manufactured Items - Items that pass through the factory that aren't end-of-production-chain products.

Products - Items that are ready for consumer sale.

Electricity - Profits made by selling excess power from power plants.

Misc. - Anything that doesn't fit in anywhere else.

EXPENSES

Payroll - All of your employee's daily wages for the month.

Benefits - All of your employee's daily benefits for the month.

Management - Management salaries.

Electricity - Amount paid to power your buildings.

Water - Amount paid to keep water flowing in your buildings

Property Tax - The amount of property tax you pay for your land over the entire globe. Land value + building value

Materials: Anything auto-bought by a building, as well as anything manually bought by the player in the market.

Transport Fees: The amount spent on chartering trade routes.

Import Taxes: Taxes paid for importing traded goods.

Export Taxes: Taxes paid for exporting traded goods.

Loan Interest: Amount paid per month to pay off the interest on your loans.

Influence: The amount paid buying influence.

Research: The amount paid to engineers and scientists to generate research points.

Land/Construction: The amount paid buying land and constructing new buildings.

Upgrades: The amount paid upgrading buildings.

Misc: Anything that doesn't fit anywhere else, as well as your IPO fee.

COMPANY SHARES:

Private Bought: This is the amount paid buying shares back from Uncle Ian.

Private Sold: This is the amount sold selling shares to Uncle Ian

Public Bought: This is the amount made when the public buys shares in your company.

Public Sold: This is the amount lost when the public sells shares in your company.

Grand Total: The math for everything. It is nice when this is green, but it being red doesn't necessarily mean that things are going badly. You've got to spend money to make money!

Only the current month and previous 5 months will be visible, and should give you a general idea about how things are going.
I am hoping to someday break this down by country, so that you can get even more in involved in tracking down where your money is going or coming from.

DD14: Objectives

DD15: New Game Options

DD16: Character Creation

DD17: Uncle Ian

DD18: ???