My suggestion concludes of an NPC and/or a command (The Banker or /banker) to redirect in a GUI where you can buy tax shares. You can only buy shares once you have reached a high enough level to negotiate with the Banker. (Prestige 2 seems like a good middle ground)
How shares work:
Every tax system in the game, eg. Charity tax, AM tax, or CF tax, should be split into the shares managed by the Banker, who offers 100 Money shares (Coinflip and AM tax) and 100 Token shares (Charity tax). These shares can be purchased with money (Preferably to be a little expensive as this is meant for high levelled players, which may already have plenty of money), and each player can have a maximum of 3-5 shares to leave space for the others. Once in a while they can collect their shares by talking to the Banker and receiving the income from tax payers. It would be a good money spending alternative rather than only advancements and it would become a good secure passive income.
Thank you for your time!