PHILADELPHIA (AP) — The co-owner of a Philadelphia-area restaurant chain will serve time behind bars for his role in multimillion-dollar tax evasion scheme.

A federal judge sentenced 75-year-old Robert Mattei to 15 months in prison on Monday. He had pleaded guilty to conspiracy, tax evasion and bank fraud.

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Authorities say Mattei and four co-defendants who ran the Nifty Fifty’s eateries engaged in a long-running scam to avoid paying taxes.

Prosecutors say the five co-owners failed to account for more than $15 million in receipts between 2006 and 2010, thus evading $2.2 million in federal employment and personal taxes.

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The four others have also pleaded guilty and are scheduled to be sentenced this week in Philadelphia.

The chain of 1950s-themed burger joints has locations in Pennsylvania and New Jersey.

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