'Vanderpump Rules' Star Jax Taylor -- Sues Shoe Company ... You Owe Me Big For Wearing Your Kicks

Jax Taylor is in a legal battle with a shoe company he claims agreed to pay him to wear its gear, and now he's taking them to court.

According to legal docs ... the "Vanderpump Rules" star reached an agreement with XCALIBUR SHOES in 2014. The agreement says in exchange for endorsing the shoes, Jax would receive $20 for each pair sold in his collection. He would also be given 10% of the total net sales he generated.

However, according to Jax, XCAL has gone sour on their end of the deal -- failing to pay him at least $25,000. He also says the bum deal has made it hard for him to find similar work ... since XCAL's competitors won't want to work with him now.