Sodium 4-hydroxyphenyl phosphate is primarily used as a substrate in biochemical assays for detecting phosphatase activity, such as alkaline phosphatase, where it undergoes hydrolysis to release 4-hydroxyphenol, which can be measured spectrophotometrically. It serves as a key reagent in research on enzymatic dephosphorylation processes and phosphorylation-related metabolic pathways. Additionally, it acts as an intermediate in the synthesis of phosphorylated organic compounds for pharmaceutical and agrochemical development.