Though a number of excellent papers have been published dealing with titration error in acid-base chemical systems of the monoprotolytic kind, the estimation of titration error of polyprotic acid (or polyacid bases and ampholytes) have received a scarce attention. Nevertheless, using the dissociation and formation (ñ) functions the chemical complexity involved in such kind of calculations is reduced considerably. Simple general expressions, based on the inverse approach for titration curves, i.e., V=f(pH), are derived for titration error of polyprotic acid (HNA), polyprotic bases (B or NaNT) or ampholytes (NaN-xHxT), in the nthequivalence point (1 to N for polyprotic acid or base, and 1 to x (or N-x) for ampholyte titrated with strong base (strong acid)). Among possible analytical applications the determination of acetic acid in vinegar, phosphoric acid in Coca-Cola, and vancomycin purity in batches of raw material were selected for study.