The former controller at Bernard L. Madoff’s investment firm pleaded guilty Monday to participating in Madoff’s fraud.

Enrica Cotellessa-Pitz, 53, pleaded guilty to conspiracy, falsifying books and records, and making false filings to the Securities and Exchange Commission. She faces up to 50 years in prison.

According to a charging document, Cotellessa-Pitz helped Madoff cheat on his taxes, and she and others altered stock-trading records for audits.

In addition, Cotellessa-Pitz doctored records to disguise money transfers from Madoff’s investment advisory business — where the Ponzi scheme was taking place — to another side of his business devoted to market making and proprietary trading, the document said. That side of the business was run by Madoff’s sons.

The transfers — hundreds of millions of dollars over about a decade — made those operations appear profitable when they were not, according to the document.

Attorneys for Cotellessa-Pitz and Madoff’s sons, one of whom committed suicide, did not respond to requests for comment.

Madoff is serving a 150-year prison sentence for cheating investors out of billions of dollars.