Debits in sales ledger control account increase total customer balances Steps:

• Recognize sales ledger control account summarizes debtors (amounts owed by customers).
• Note debit entries increase debtors (e.g., sales, interest); credit entries decrease them (e.g., payments, write-offs).
• Analyze each option: does it increase or decrease total owed amounts?
• Match to standard accounting: only increases qualify as debits.

Why C is correct:

• Interest charged adds to the customer's outstanding balance, increasing total debtors per double-entry rules (debit control account, credit interest income).

Why the others are wrong:

• A. Contra entry offsets debtor balance against creditor, decreasing net debtors (credit entry).
• B. Irrecoverable debt write-off removes uncollectible amount from debtors (credit entry to control, debit expense).
• D. Sales returns reduce the amount owed by customers (credit entry to control).

Final answer: C