WASHINGTON—KPMG LLP is preparing to pay as much as $50 million to settle civil claims related to the conduct of former partners who learned which of their audits would be subject to surprise regulatory examinations, according to people familiar with the matter.

The fine would be one of the highest ever imposed on an auditor in a Securities and Exchange Commission action. The details could change as agency commissioners debate the final details of the settlement.

The SEC and prosecutors pursued civil and criminal charges against five former KPMG officers and a former regulator in January 2018 for sharing confidential information about which of the firm’s audits would be examined by its primary regulator, the Public Company Accounting Oversight Board. The regulator discovered a leak in February 2017, and KPMG fired the partners a couple months later.

Congress created the accounting board to inspect the work of public-company auditors after the accounting scandals that blew up Enron Corp. and WorldCom. The SEC oversees the board’s work and retains the ability to police auditors on its own.

A federal jury in March convicted the most-senior former auditor involved in the matter, David Middendorf, who was KPMG’s national managing partner for audit quality. It also convicted a former board employee, Jeffrey Wada, who gave KPMG officials a confidential list of audits to be inspected. Mr. Wada referred to the inspections as “the grocery list,” according to law-enforcement officials. Both criminal convictions included conspiracy and wire fraud.