According to the invention, there is provided a novel soybean variety, designated XB55K04. This invention thus relates to the seeds of soybean variety XB55K04, to the plants of soybean XB55K04, to plant pads of soybean variety X855K04 and to methods for producing a soybean plant produced by crossing soybean variety XB55K04 with another soybean plant, using XB55K04 as either the male or the female parent. This invention also relates to methods for introgressing a transgenic or mutant trait into soybean variety XB55K04. This invention further relates to soybean seeds, plants, and plant parts produced by crossing the soybean variety X855K04 with another soybean variety.