tax question for COMC returns

[boxbuster7]

So lets say as a seller I had:

$300 in returned cards from COMC last year

On a normal sale they take 5% in fees. On a return they give back the 5% they take from the seller to the buyer.

I report returns as an expense because the original sales are included in my total sales figure

I had been subtracting the 5% transaction fee and claiming $285 in returns as an expense.

Is this correct?