Deductions & credits

Not really.  If you enter your total gross receipts before the discount then you can expense the discount.  Or enter the actual income you received and don't enter the discount.  Works out the same.  Example:   Total bill 1,000 with 100 discount.  Either enter 1,000 as income then enter 100 discount equals 900 net income.  Or just enter 900 as income received and don't enter discount, equals 900.