I have also had this issue as well. It seems to be better once I downloaded the "mods" (script files from Pocus as a manually applied patch). There is a mod for Admin Burden, and Trading Factors, as well as one about ships. Here is the admin burden fix link and the other 2 mods are in threads ...

Some possible reasons:
1. trade deals were accepted in which you sent gold to the other side
2. regional decisions came into effect
3. random events cost you gold


No trade deals sending gold to the other side (I never give them gold)

What regional decisions can make me lose money?

The same ...

Playing Rome the estimated money income does not correspond to the money received.

https://i.postimg.cc/8c5qGzpJ/FIELDOFGLORYEMPIRES-28-07-2020-8-26-19.png

Next turn. Zero expenses. No battles

https://i.postimg.cc/4dFWzbGy/FIELDOFGLORYEMPIRES-28-07-2020-8-28-56.png

Estimated money income ...