So I changed the default currency to gold:

currency:
name:
singular: Gold
plural: Gold
named-denominations: false
denominations:
- material: gold_nugget
value: 0.2
- material: gold_ingot
value: 1.8
- material: gold_block
value: 16.2

I'm using Towny and I can make a town with the gold, but when I try to make a nation it tells me I don't have enough. I also can't donate to the town bank or use any monetary function of my created town.

Having the same issue. Seems to occur only when money is being transferred to another account.

Having the same issue. Seems to occur only when money is being transferred to another account.

I realized that the solution is a sign with [vault] on either a chest or a block directly behind it. I think you might need the vault plugin for it, but I could be wrong.