AI've made a butter cream cake. I was wondering does it need to go in the fridge. I'm making it the day before Thanks in advance

AI store all my cakes in the fridge

Depending where you live - in general- NO you do not have to frig a b'cream cake.  Of course one has to consider the filling used.  That is the more important consideration.  Then are you in a very humid location - that your home is very humid.  That would be the next consideration. 

AI never store cakes in the fridge. But I don't use perishable fillings either.