Santander Consumer USA Holdings delayed the filing of its annual report Monday amid discussions with the Securities and Exchange Commission regarding unresolved accounting issues.

The Dallas-based auto lender notified the SEC that it plans to submit its annual report, known as a 10-K, after Monday's filing deadline.

Laurie Kight, a spokeswoman for Santander Consumer, said in an email that the company plans to file the annual report by the March 15 extension deadline.

Monday's filing stated that Santander Consumer's financial statements have yet to be completed. It also noted that Santander Consumer has yet to resolve an inquiry by the SEC related to the firm's credit-loss allowance.

The filing suggests that the SEC has questions about a change, announced in October 2015, in how Santander Consumer determines its quarterly provision for credit losses.

During the company's third-quarter 2015 earnings call, executives said that the accounting change would help the firm adjust for seasonality in its business.

As a result of the change, Santander Consumer's loss provision shrunk by $134 million in the third quarter. Profits rose by 17% from the same period a year earlier.

The change came at a time when Santander Consumer's loss provision had been steadily rising, as the subprime lender targeted auto buyers with blemishes on their credit records.

The auto lender's latest filing said that the unresolved matters with the SEC involve the company's quarterly report for the period ended Sept. 30, 2015, as well as its 2014 annual report.

The filing referred to an "open comment letter" with the SEC "with respect to the company's credit-loss allowance, including the removal of seasonality and the increase in troubled-debt restructuring" impairment during the third quarter of 2015.

Since October, the credit quality outlook in subprime auto lending has continued to worsen. In announcing its fourth-quarter results, Santander Consumer warned investors that chargeoffs could increase during 2016.

In January, the industrywide percentage of securitized subprime auto loans that were at least 60 days delinquent hit 4.98%, its highest level since September 2009, according to Fitch Ratings.

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