There are 2 calculation formulas for days in AR: The simple method and the countback method. Determine the days' sales in receivables for 20Y9 and 20Y8.Assume 365 days in a year. Average days delinquent (ADD) is a metric that lets companies know the average number of days that late payments take to get collected. Learn how to calculate the average days sales in accounts receivable and tips for interpreting the results. With yearend quickly approaching, here are accounts receivable best practices to help your accounting team close out the books. The following table provides additional summary stats. Airbus's latest twelve months days sales outstanding is 36 days.. View Airbus Group NV's Days Sales Outstanding trends, charts, and more.