Revenue recognition and impairment for goodwill and long-lived assets were among the areas where PwC LLP auditors fell short, according to the firm’s most recent annual review.

The Public Company Accounting Oversight Board determined that the firm didn’t have enough evidence to issue its audit reports in 13 engagements reviewed, according to the firm’s 2017 inspection report released March 28.

Fifty-five audits were inspected. The results are similar to the firm’s 2016 report, which found deficiencies in 11 out of 56 audits inspected.

As a result of the inspection findings, a PwC client adjusted its financial statements. The firm also reversed its opinion on the effectiveness of a client’s internal controls for financial reporting.

PwC said that performing high-quality audits is the firm’s top priority. It detailed steps the firm is taking to improve audit quality including investing in its staff and audit technology.

According to the report, the firm didn’t verify that the revenue for a client’s domestic segments was legitimate and didn’t sufficiently test controls related to cash sales for a retailer. In addition, it didn’t test the accuracy of a spreadsheet used by a client to assess the value of its excess and obsolete inventory.

PwC auditors also ignored oil and gas industry information that contradicted an industrial company’s forecasted oil prices.

PCAOB inspectors review audits with the highest risk and most complex accounting. The board plans to update its inspection reports to provide a more balanced view of a firm’s auditing.