Union dues are the cost of union membership. Usually union members need to make the regular payment of money to fund the various activities which the union engages in.
ezPaycheck payroll software is very flexible. As an employer, if you need withhold union fee from the employees’ paychecks, you can use the customized deduction feature.
You can refer to this article for step by step guide on how to add a customized deduction by percent and withhold it from each paycheck automatically.
http://www.halfpricesoft.com/business-blog/post/2011/05/05/How-to-add-a-new-payroll-deduction.aspx

