A rotating assembly (20; 20') for a gas turbine engine, comprising: a first rotating component (22i'; 22i") mounted on a shaft for rotation about an axis (11; GC); and at least one balancing ring (26a, 26b; 26a', 26b') mounted to the first rotating component (22i'; 22i") and clocked at a circumferential position about the axis (11; GC) to counteract a rotating unbalance of the first rotating component (22i'; 22i"), the at least one balancing ring (26a, 26b; 26a', 26b') having a smooth circumferential surface engaged with a corresponding smooth circumferential seating surface on the first rotating component (22i'; 22i"); characterised in that the rotating assembly (20; 20') comprises: a spacer (22j'; 22j") mounted on the shaft and axially abutted against the first rotating component (22i'; 22i") to set an axial position of the first rotating component (22i'; 22i") relative to a second rotating component (22k'; 22k") of the rotating assembly (20; 20'), the second rotating component (22k'; 22k") being mounted on the shaft, the spacer (22j'; 22j") locking the at least one balancing ring (26a, 26b; 26a', 26b') against rotation relative to the first rotating component (22i'; 22i"), wherein the spacer (22j'; 22j") is axially clamped between the first and second rotating components (22i', 22k'; 22i", 22k"), wherein the spacer (22j'; 22j") and the at least one balancing ring (26a, 26b; 26a', 26b') have a circumferential interface with cooperating anti-rotation male/female portions (34, 36a, 36b). a first rotating component (22i'; 22i") mounted on a shaft for rotation about an axis (11; GC); and at least one balancing ring (26a, 26b; 26a', 26b') mounted to the first rotating component (22i'; 22i") and clocked at a circumferential position about the axis (11; GC) to counteract a rotating unbalance of the first rotating component (22i'; 22i"), the at least one balancing ring (26a, 26b; 26a', 26b') having a smooth circumferential surface engaged with a corresponding smooth circumferential seating surface on the first rotating component (22i'; 22i"); characterised in that the rotating assembly (20; 20') comprises: a spacer (22j'; 22j") mounted on the shaft and axially abutted against the first rotating component (22i'; 22i") to set an axial position of the first rotating component (22i'; 22i") relative to a second rotating component (22k'; 22k") of the rotating assembly (20; 20'), the second rotating component (22k'; 22k") being mounted on the shaft, the spacer (22j'; 22j") locking the at least one balancing ring (26a, 26b; 26a', 26b') against rotation relative to the first rotating component (22i'; 22i"), wherein the spacer (22j'; 22j") is axially clamped between the first and second rotating components (22i', 22k'; 22i", 22k"), wherein the spacer (22j'; 22j") and the at least one balancing ring (26a, 26b; 26a', 26b') have a circumferential interface with cooperating anti-rotation male/female portions (34, 36a, 36b). a spacer (22j'; 22j") mounted on the shaft and axially abutted against the first rotating component (22i'; 22i") to set an axial position of the first rotating component (22i'; 22i") relative to a second rotating component (22k'; 22k") of the rotating assembly (20; 20'), the second rotating component (22k'; 22k") being mounted on the shaft, the spacer (22j'; 22j") locking the at least one balancing ring (26a, 26b; 26a', 26b') against rotation relative to the first rotating component (22i'; 22i"), wherein the spacer (22j'; 22j") is axially clamped between the first and second rotating components (22i', 22k'; 22i", 22k"), wherein the spacer (22j'; 22j") and the at least one balancing ring (26a, 26b; 26a', 26b') have a circumferential interface with cooperating anti-rotation male/female portions (34, 36a, 36b).