It's a point that is constantly argued and constantly changing. I took the Payroll administration courses, and am so certified, but even the teacher at that course told us that year by year, so many of the rules, such as this one, change, that only someone with an up-to-date labour taxation and payroll guide, or whatever they call it this year, would know. Your best bet to get a straight answer would be to contact your local MP's constituency office and ask them to check up on it, or ask them where you can check.
Good Luck!
ViolaB