It is often convenient to arrange for the purchaser of a business to collect outstanding receivables. If the vendor sells say $100,000 of debtors to the purchaser for $90,000, the $10,000 difference is a capital loss. If the purchaser collects $91,000, he/she makes a tax free gain of $1,000, providing there is no scheme or the purchaser is not in the business of buying and selling debts.
The better way, if it suits from a cash flow perspective, is to let the purchaser collect the debts and pay a percentage fee for the service. Thus $100 collected might net you $96 but the $4 difference is tax deductible.