'Cash purchases' means any payment you make to suppliers of goods or services with whom you do not have an account. As you don't have an account, you will have to pay for the goods or services at the time when you buy them.
For example, you might send off cash with order for a specialist publication or use a credit/debit card to buy computer supplies from an online supplier.
Cash purchases don't include things like tea and coffee bought for use at work, or items such as business stationery.
Remember to keep safely all the invoices and receipts for Cash purchases, even if the amounts are small.