Do you have any references for further reading on this topic? And how is a wage tax different from an income tax? It might not show up on an employee's payroll

Do you have any references for further reading on this topic? And how is a wage tax different from an income tax? It might not show up on an employee's payroll, but the end result is the same, no? And if you're not taxing capital/capital gains in any way, won't this cause inequality to shoot up even more than it already is?