You need tax offices to get money from taxes.

Also, most likely you're losing that much money from roadbuilding. It's currently very expensive to build multiple roads at once.

Are you building a lot of stuff in those towns at one time? Same thing happened to me in one of my games. As you cue up buildings the cost for them is added up and subtracted from your gold total. You'll notice as a building finishes your income will go back up. Check through your cities and see if you're building a lot at once. If so cancel those buildings and build the most important ones first one at a time and see if this helps.

aven X is right insofar that it hurts to que buildings up. If you order 4 houses built you pay for them in one single payment. Obviously for the first house this is good because the building starts at once, but for the other 3 houses you pay money and get no returns for a long, long time.

Building one bilding at a time is the way to go, but it is micro-heavy. I would very much prefer it if the money was substraced when the buildings commenced rather than when the building is ordered.

Also  would very much prefer it if there was a 'manual labor'  resource or something similar so that certain buildings would not cost money. Why would a house be funded by the nation's treasury? Your people should be motivated to build houses for themselves, right?

I guess I figured out what my problem was. Once you make a 6th city your 'city upkeep' costs go sky high afterwards. The fact that population generates no tax income makes it hard to pay the bills. But if you make a 7th and 8th city right now, you will be paying huuuge upkeep costs.

Wonder when taxation will be going in.