The rapper will get an advance of over £1 million from EMI music publishing for his songwriting on future albums. He'll receive the rest following the release of the records, The Sun reports.
The contract doesn't include earnings from The Defamation Of Strickland Banks or new album iLL Manors, which is released on July 23.
"It's a huge deal for Ben, worth a lot of cash. There aren't many artists who get these kind of offers nowadays but his success with Strickland Banks has earned him kudos," a source said.
"He'd just got out of an old publishing deal and EMI had been trying to get him to sign on with them for ages.
"It comes on top of a joint venture he launched earlier this year with EMI which will see him scout for new writing talent."
Watch Plan B discuss iLL Manors below: