Minting

From EU3 Wiki

Minting is a process of producing currency from your monthly income. The ducats are added to your treasury but the downside is that minting increases inflation.

A common strategy is to rely on annual income in increasing the treasury as it is inflation-free income and mint only a little or not at all to keep the inflation low. However events in the game may require players to raise larger sums of ducats for short periods of time (for war expenses for example), which often forces players to mint ducats and sacrifice long term goals for immediate need.