Calibration of force transducers in the Meganewton range is typically performed by comparison with reference build-up systems (BUS) under hydraulic presses for high loads. The centring of a BUS isa difficultoperation due to itsweight and dimension, andpossible misalignmentsand the resultingeffects are usually neglected.In this work the effect on force measurements due toa 3 mmmisalignment of a 3 MN BUS wasevaluated.Measurements were performed at INRiM and at LNE in hydraulic presses.Itis shown that the relative measurement errorsdue to misalignment were lowerthan the declared CMC uncertainty,thus the shiftof the BUSdid not influence the measurements.