A system (100, 100e, 100f) for reducing weighing errors of an item (1710, 2400) being weighed on a weigh platter of a scale associated with a data reader (180, 190) installed in a checkout counter surface or other fixed object, the system comprising: a weigh platter including a top surface adjacent the checkout counter surface or other fixed object, the top surface of the weigh platter including a first lateral edge (2330a, 2330b) that is adjacent a first edge of the checkout counter surface or other fixed object; a data reader (180, 190) configured to detect a change in light reflected from a region (2320a, 2320b) proximate the first lateral edge of the top surface of the weigh platter; a controller (240, 2310) coupled to the data reader (180, 190), the controller (240, 2310) configured to determine whether an item rests partially on the checkout counter or other fixed object and partially on the weigh platter based on whether the item (1710, 2400) blocks a portion of the light that would otherwise reflect off of said region (2320a, 2320b) proximate the first lateral edge; characterised by a first reference pattern (1500a, 1500b, 1700a, 1700b, 1900a, 1900b, 2000a, 2000b) positioned on the top surface of the weigh platter proximate and along the first lateral edge (2330a, 2330b), wherein the data reader (180, 190) is configured to detect the first reference pattern (1500a, 1500b, 1700a, 1700b, 1900a, 1900b, 2000a, 2000b) when the first reference pattern is unobstructed by an item (1719, 2400) and the controller (240, 2310) is configured to determine whether an item (1700, 2400) blocks a portion of the light that would otherwise reflect off of the region (2320a, 2320b) proximate the first lateral edge of the top surface of the weigh platter based on whether the item interrupts the first reference pattern. a weigh platter including a top surface adjacent the checkout counter surface or other fixed object, the top surface of the weigh platter including a first lateral edge (2330a, 2330b) that is adjacent a first edge of the checkout counter surface or other fixed object; a data reader (180, 190) configured to detect a change in light reflected from a region (2320a, 2320b) proximate the first lateral edge of the top surface of the weigh platter; a controller (240, 2310) coupled to the data reader (180, 190), the controller (240, 2310) configured to determine whether an item rests partially on the checkout counter or other fixed object and partially on the weigh platter based on whether the item (1710, 2400) blocks a portion of the light that would otherwise reflect off of said region (2320a, 2320b) proximate the first lateral edge; characterised by a first reference pattern (1500a, 1500b, 1700a, 1700b, 1900a, 1900b, 2000a, 2000b) positioned on the top surface of the weigh platter proximate and along the first lateral edge (2330a, 2330b), wherein the data reader (180, 190) is configured to detect the first reference pattern (1500a, 1500b, 1700a, 1700b, 1900a, 1900b, 2000a, 2000b) when the first reference pattern is unobstructed by an item (1719, 2400) and the controller (240, 2310) is configured to determine whether an item (1700, 2400) blocks a portion of the light that would otherwise reflect off of the region (2320a, 2320b) proximate the first lateral edge of the top surface of the weigh platter based on whether the item interrupts the first reference pattern.