You may be able to encourage customers to pay you more quickly. For example, you could offer a discount for cash payment.
You should also consider whether you can free up any of the other money you have tied up in working capital. For example, you might sell off old stock, control your purchases more closely or ask your own suppliers for extended credit terms.
You may also want to look at financing options, such as factoring or invoice discounting. This allows you to receive most of the value of outstanding invoices without waiting for customers to pay. Factoring may well be an option if your annual credit sales are at least £50,000—£100,000 and are not concentrated with a handful of customers.
If you cannot reduce your cash flow problems in any of these ways, you may have to consider restricting credit sales: even if that means slowing the growth of your business and reducing profits. Overtrading beyond the turnover your cash flow can support is a common cause of business insolvency.