The Sales Ledger Control Account (Debtors Control Account) is built up during the year from total credit sales, cash received, discounts allowed, returns inward, bad debts, and similar movements affecting debtors, and it mirrors, in total, every individual customer account kept in the sales ledger.
Whatever balance remains on this account at the end of the accounting year is, by definition, the total of all amounts still owed by customers that have not yet been collected, written off, or otherwise cleared. In other words, it represents the total trade debtors outstanding at that date, and this is the figure that appears as trade debtors (accounts receivable) under current assets in the balance sheet.
It is not simply the total credit sales for the year, since credit sales are only one side of the account; receipts, discounts, and returns during the year have already reduced that figure down to what is still owed. It excludes cash sales entirely, since cash sales never pass through this account at all, and it is not merely the total transferred from the Sales Day Book, which records only credit sales made, not the net amount still outstanding after collections and adjustments.
Examination reminder: the closing balance on any control account represents the net outstanding position at that date, not a single component such as sales or receipts alone.