I got UK to a positive bank balance. Didn’t notice any income arising from this. Are Sovereign Wealth Funds handled in the game at all?
I noticed this too in my Australia game. Got to $1 trillion reserves and I wasn’t getting any interest. What’s that about?
The surplus is quite simplistic, the only use for it I’ve found is to weather world recessions. I’d love to see policies that utilise the surplus, like a social dividend that divides up a percentage of the surplus (decided by slider) and redistributes it to the population. Could be a great way of replacing welfare if the economy is doing well.
There currently is no benefit to holding a reserve as far as I can tell, other then having a rainy day fund. You’re basically stuck with being the national equivalent to somebody who puts all their money in a pillow case.
The australian liberal party in government in 2007 was one financial year away from paying off the nations debt. Things were looking good for us financially and I remember thinking with child like naivety “Wow, eventually the government would be making so much money from interest, we’d never have to pay taxes!”
Unfortunately for Australians in late 2007 liberal party lost to a populist socialist party who began a spending spree during the GFC and within one year threw us into the greatest raw and %GDP debt we had ever seen.
Am SUPER disappointed to not be able to do this in game 
TL:DR Give money when holding a reserve or even an action menu for foreign investment/foreign loans/countries not paying it back!
Perhaps something like this? en.wikipedia.org/wiki/Australian … uture_Fund