The days' Receivables ratio measures the average payment terms the company grants to its customers (or the average actual payment period). It is calculated by dividing the Receivables balance by the company's average daily Sales (VAT inclusive). Days' Receivables ratio is also called days' Sales outstanding.

(See Chapter 11 Working capital and capital expenditures of the Vernimmen)

To know more about it, look at what we have already written on this subject