What cost element categories can be used for primary cost elements?

The primary cost elements include primary costs/cost reducing revenues (01), accrual/deferral per surcharge (03), accrual/deferral per debit (04), revenues (11), sales deduction (12), external settlement (22) and cost element for balance sheet accounts in financial accounting (90). Sales deduction are very useful in SD module as they help with adjustments postings such as rebates and discounts.