Taxes are the most common way to collect Silver. Taxes refresh during the server reset at a rate of 12/day(15 for Summer). There are many factors that affect your tax revenue such as how many residences you have and their levels, Tax Office level, Regional Prosperity, Loyalty and Alliance Account Research Level. At first you will not think you need much silver, but later in the game it will become one of the most important resources.
It is also important to note that even if your Loyalty reaches 0, you will still be able to collect taxes.
Refer to the Tax Event Reward List for aid with the events that appear occasionally.