They currently have tax codes set up for every county in the state. When rates change (like equipment sales rate) they are finding it very time consuming to go into each tax code and update the rate (data is doing it this time, but they don't like having to have data do it everytime they need to update in mass). They also cannot do this prior to the effective date so that is a problem that would be solved with an effective date.
Not being able to have an effective date could create compliance issues unless someone is changing those rates at midnight of the effective date (Jan 1 change must be done at midnight Dec 31 or face the chance of overcharging/undercharging a customer at unmanned fuel pumps). To have an effective date would ensure that the correct sales tax is collected at the correct time and would also avoid the possibility that a person failed to make this change at the appropriate moment.