Chip and Joanna Gaines Getty

"Fixer Upper" stars Joanna and Chip Gaines are being taken to court by their former literary agent who claims the couple tried to back out of paying a set fee for their massive book deal after signing with someone else.

According to legal docs, obtained by TMZ, Joanna and Chip were repped by Vigliano Associates when they inked a massive $12.5 million deal back in 2017 to crank out 5 books for HarperCollins.

Vigliano says it was set to get a 7.5% cut of any payments to the couple and claims everything went fine for the first 2 books ... but Vigliano says the couple then "concocted a scheme" to back out payments for the last 3 books by trying to amend the deal.

The docs say the couple tried to eliminate one of the books and, as for the other two, Vigliano says they tried to swap out Joanna and make Chip the author for one of the remaining books.

Vigliano claims the original deal only applied to Joanna-authored books, so the move essentially took the book deal from 5 books down to 3 ... and, as a result, meant much less pay for Vigliano.

Waiting for your permission to load the Instagram Media.

ncG1vNJzZmivp6x7tbnZZ5qopV9nfXN%2BjmppaGhnZLewrc2nmGafkZ67pr%2BMnJ%2BiqF2owqZ5y6KrnqqRp8Zurcaepa1lkqS8rHnDnpilZZaexaa%2BjK6nqZ2iYrWowNVo