The assurance of sustainability reports and their impact on stock market prices

The publication of non-financial information is a trend in recent decades in listed companies. From this fact, the need arises to provide credibility to the information by verifying an independent professional who provides a guarantee of the published information. Therefore, this article analyses whether the verification of sustainability reports influences the stock prices of Ibex-35 companies. With this aim, a content analysis has been prepared that allows us to quantify aspects as relevant as the commissioning and the objective of the assurance requested by the company, the auditor’s independence or the result of the verification process. The results obtained show that Ibex-35 companies maintain a growing trend in their social commitment and greater recognition of the transfer of verified information to the different stakeholders of the companies. In addition, the efforts made by companies are valued positively by investors, especially in response to the level of assurance requested from the guarantee provider of the sustainability report.