Q. How much should I charge for my cakes ?
A. You’re only allowed to charge for the cost of ingredients for cakes made on an “occasional basis” for “friends & family”.
If you; 1) charge more than the cost of ingredients, or 2) sell to the public or 3) do it regularly or have repeat orders then you’re acting as a business and consequently must be registered with the Environmental Health department of your local council (www.food.gov.uk), have Public Liability Insurance in place and declare any profits made to HMRC (www.hmrc.gov.uk).
My advice (a bit harsh I know) is that if you’ve gone to the trouble of starting a business then you should at least be able to work out profit margins, cost of ingredients, etc without having to ask how much you should charge for a cake - otherwise your business won’t last that long.
Also: If you provide food to the public then you need to make sure that the food is safe.
Best way to do this is to register with your local council. They will provide you with all the info you need.