I have to pay gas safe register to register with them every year and when I notify them an appliance has been fitted, does this go down under professional fees?
I would put it in as licences or create a new overhead nominal for it. It doesn't make any real difference to your year end accounts and you could use professional fees. I tend to use this for solicitors,accountants etc but different people will have different opinions. The key is to be consistent, whichever you chose stick with it.