Credits are rather unique in that they’re both acquired and spent in many more ways than Manufacturing, Food, Control or any of the other in-game resources you’ll come across. Credits are gained by taxation, through Trade Routes, diplomatic exchanges with other players, selling Strategic Resources at the Bazaar and as a consequence of the many varied Events that crop up during the game.
So, how exactly are Credits generated via taxation? Here follows a very brief and simplified rundown, if you want more detail, I’ll point you to the developer blog video I made covering the economy here.
Core Worlds and attached Colonies have a Planetary Input value called Wealth Input, representing the riches on and flowing into the planet. Citizens, Financial Districts and certain Improvements further modify this value, representing combined on-world commercial activities.
Your tax-rate, set at the top level with the one rate affecting your entire Civilization, is then applied to this modified Wealth Input value as a multiplier to become a Core World’s Income.
The sum of your Core World’s Income is shown on the Civilization Overview screen too, where you can see your Civilization’s GDP (summed Income) before it’s modified by tax.
You can also see that you make Credits from the Trade Routes you set up by sending a Freighter from one of your Core Worlds to one owned by your neighbors. You can see the Trade Route UI below, with all the current Trade Routes set up between yourself and your trade partners.
Going back to the Civilization Overview screenshot, you can also see some of the things Credits are spent upon: maintenance for your Ships, Colony Maintenance (stuff you’ve built on your Core Worlds), Starbases and the Credit cost of an Civilization Policies you have set.
Credits can be used for barter in diplomacy, either to acquire other goods or to sweeten a Treaty proposal. Not sure I like this deal much though, those Navigators don’t seem very willing to part with their Credits here.
This is simple stuff: sell whatever you’re willing to part with for Credits when you’re in need of them, and if you’ve got extra Credits to spare, you can buy Techs, Strategic Resources, Diplomatic Capital and other useful things from those that have them.
If you have excess Strategic Resources, you can sell them at the Bazaar in exchange for Credits, which is the preferred barter resource for the aliens who run it. Here they’re offering 83 Credits for each Aurorus Arboretum. Sadly, I don’t have any. Be aware that repeatedly selling the same resource will devalue that stock and reduce the Credits you’ll receive for each unit.
Certain Events, such as finding exotic Artifacts, modules or useful space junk, will give you the option to sell your new acquisition for Credits. This can make Survey a profitable endeavor for much of the game, so don’t neglect those Flag Ships!
With the Credits earned from selling that Armor Module, Lord Kona can rush build a warship he needs. This will cost a lot of Credits but the faster you build your military, the stronger you’ll be. This will also cost some Control, and you’ll take a hit to your Approval too as your Citizens don’t much enjoy being forced to work long overtime, even if they are being paid extra for it.
Building a large treasury of Credits can be handy, as you’ll notice that Credits are used as a shortcut to gaining certain things a lot faster than you’d be able to without that cash injection: quickly gaining Techs through diplomacy, rush building Ships, Districts or Improvements, buying Strategic Resources from the bazaar and more.
Credits are such a ubiquitous resource that I’ve likely missed some of their more subtle uses here, but I hope this has clarified just how you can make and spend them.
