Audit regulators have published the last of the major 2015 inspection reports showing a little more than half of the audits inspected at BDO USA contained deficiencies, several so significant they led to restatements and withdrawn internal control opinions.

The Public Company Accounting Oversight Board says inspectors in 2015 selected 23 audit files for scrutiny at BDO and found fault in 12 of them, or 52 percent. That’s the highest rate of busted audits for any of the major firms that year, but still an improvement for BDO over its 2014 results, which reflected a failure rate of 74 percent.

Of the 12 BDO audits called out by the PCAOB in 2015, three revealed deficiencies in the financial statement audit that failed to uncover accounting anomalies so serious, they ultimately led to restatement. Inspection revelations in three of the 12 failed audits also led the firm to withdraw its opinions on the effectiveness of the company’s internal control over financial reporting. The PCAOB report does not specify whether that involved six separate audits, or whether some of those restatements and withdrawn opinions may have occurred within the same set of financial statements.

In BDO’s letter to the PCAOB included in the report, the firm says it took appropriate measures on each of the findings and remains committed to audit quality. “The PCAOB’s inspection process assists us in improving our audit performance and our underlying quality control systems,” the firm said. “We look forward to continuing to work with the PCAOB on the most effective means of achieving this objective.”

In terms of inspection findings leading to restatement, only PwC posted numbers in 2015 to rival BDO’s performance. At PwC, inspectors pored over 55 audit files and found deficiencies in 12 of them, or 22 percent. Within those dozen blown audits, however, the firm withdrew its opinion on internal control in six cases, and two issuers ended up restating their financial results. PwC’s restatement rate arising from inspections has been similarly high in prior years, with four withdrawn opinions and one restatement of financial statements in 2014, which followed five withdrawn opinions and four restatements in 2013.

Across the largest firms in 2015 — that includes the Big 4, plus Grant Thornton and BDO USA — the PCAOB inspected a total of 274 audit files and found fault with 87 of them, or 32 percent. After BDO’s 52-percent deficiency rate, Grant Thornton logged a 41-percent deficiency rate followed by KPMG at 38 percent. Despite the number of restated or withdrawn opinions at PwC, the firm had the lowest percentage of failed audits at 22 percent, followed by Deloitte at 24 percent, and EY at 29 percent.

The PCAOB is gearing up for its 2017 inspection cycle, dispatching auditors for field work on 2016 financial statement audits. Reports on 2016 inspections of 2015 financial statements have not yet been published.

KPMG recently dismissed key audit leaders after learning of a leak of confidential information at the PCAOB regarding which audits had been selected for inspection, giving audit partners an opportunity to double check their work before inspectors would arrive. The PCAOB also indicated it dismissed someone as well. Neither the PCAOB nor the firm has explained how the leak affected either historic inspections or inspections that will take place in the coming cycle to assure fair and transparent results for all firms.