The assumption has been that last year’s Summer Sale from the US Postal Service produced $24.1 million in net revenue growth but, that may not be the case. According to a new audit from the USPS Inspector General, the sale may have in fact lost $39.6 million in revenue.  A second Summer Sale is currently taking place. The Summer Sale program, which ran between July 1 and September 30 last year, provided mailers a 30% credit for additional volume mailed over a specific threshold. However, because the US Postal relied on customer-provided data to determine thresholds, it did not always have independent, reliable and complete data upon which to calculate any revenue or volume increases from the sale, according to the report. In addition, because the US Postal Service and the Postal Regulatory Commission use different methods for determining customer mail volume, the report – which relies on the PRC method – found that the US Postal Service may have provided $67.8 million in rebates inaccurately. The report also found that the US Postal Service did not include all expenses associated with employees who worked on the project. The US Postal Service said the report didn’t reflect the intangible benefits of the Summer Sale, which included promoting customer business, retaining customers and rewarding loyal customers. The US Postal Service also said that it implemented processes in June to lessen its reliance on customer data as well as track employee and contractor costs for the 2010 Summer Sale. The USPS is also developing better technology for collecting customer data. It expects to implement the first phase of the projected three-tiered technology enhancement project during the third quarter of 2011. Read the full report, including the US Postal Service’s comments, here.