8:41 (You ask about the distribution of the spoils of war when you fight aggression and attain victory.) Whatever you take as spoils of war, a fifth of that is for God and the Messenger (the State). (And the rest) is for the families (of the fallen soldiers), those left alone in the society, the widows, the ones whose income has stalled for any reason, and the needy wayfarer, the homeless son of the street. This (you will do) if you believe in God and in what We have revealed to Our servant when the two armies met (at Badr) on the Day of Distinction. God has appointed due measure for all things and events. [Families of the slain soldiers are included in context]
Can we take the above to mean tax rate is 20% to state and everything else we earn may be used by ourselves with whatever excess given to the needy if we wish?
State uses taxes for its bureaucracy and major infrastructure projects, health, education...? If we give excess to improve our lives and of others, good incentive to give freely and appropriately.