This dissertation aims to apply a methodology to assess the maximum allowable differences in LPG custody transfer operations for each particular operation, using hypothesis tests based on measurement uncertainty, as opposed to using pre-established values in metrological standards and technical regulations. Such documents propose a single value for maximum uncertainty in custody transfer measurements, without establishing maximum permissible differences in operations between two systems, leaving it up to suppliers and customers to negotiate this parameter, which often causes disputes. The results showed that in an isolated system, unlike other methods, environmental conditions do not influence the mass measurement method and its uncertainty. No maximum permissible difference of transferred mass of LPG between tank trucks and measuring stations exceeds 1.0 percent; in contrast, when a storage sphere is part of one of the measuring systems, this parameter completely depends on the operating conditions and definitely a single value should not be considered.