The best way to fund a UBI is to have a tax on Dollars. Having a tax on Dollars is a fair tax that treats every Dollar the same no matter who currently possesses it. When paired with a UBI, the tax on Dollars guarantees a percentage of the total stock of Dollars is always flowing to UBI cash payments. This is more stable than taxes based on GDP or investment activity.
Practically, if you possess an average amount of Dollars, the tax on Dollars and the UBI cancel each other out. If you have no Dollars then you pay no tax and receive a UBI. If you have a million Dollars then you pay more in Dollar Tax then you receive from the UBI. The result, in everyone’s accounts, is a tendency towards having an equal, average, amount of Dollars.
The roughly average amount of Dollars in our accounts is a measure of our “equality.” The average amount of Dollars can be considered a Ballot because there is one average amount of Dollars per person in the system. The Ballot is divisible and denominated in Dollars. And the UBI and Dollar Tax is the election process. It enforced the term. It is a Republic!