A computer-implemented method of generating machine marking instructions for marking an ophthalmic lens, the method comprising the steps of: receiving lens order data related to a lens order and an initial marking layout; calculating, using the lens order data, ophthalmic lens data of an ophthalmic lens related to the lens order; determining, using the ophthalmic lens data, marking parameters relating to the ophthalmic lens; producing an additional marking layout by modifying the initial marking layout using the marking parameters and the lens order data, the additional marking layout representing the markings to be applied to the ophthalmic lens; and generating machine marking instructions arranged to cause a marking machine to mark the ophthalmic lens in accordance with the additional marking layout, wherein the step of producing an additional marking layout further comprises the steps of: producing a final marking layout, by modifying the initial marking layout using the marking parameters and the lens order data, the final marking layout representing the markings to be present on the ophthalmic lens; characterized in that the step of producing an additional marking layout further comprises the steps of: receiving a semi-finished marking layout representing the markings applied to a semi-finished lens; and producing the additional marking layout by subtracting the semi-finished marking layout from the final marking layout. receiving lens order data related to a lens order and an initial marking layout; calculating, using the lens order data, ophthalmic lens data of an ophthalmic lens related to the lens order; determining, using the ophthalmic lens data, marking parameters relating to the ophthalmic lens; producing an additional marking layout by modifying the initial marking layout using the marking parameters and the lens order data, the additional marking layout representing the markings to be applied to the ophthalmic lens; and generating machine marking instructions arranged to cause a marking machine to mark the ophthalmic lens in accordance with the additional marking layout, wherein the step of producing an additional marking layout further comprises the steps of: producing a final marking layout, by modifying the initial marking layout using the marking parameters and the lens order data, the final marking layout representing the markings to be present on the ophthalmic lens; characterized in that the step of producing an additional marking layout further comprises the steps of: receiving a semi-finished marking layout representing the markings applied to a semi-finished lens; and producing the additional marking layout by subtracting the semi-finished marking layout from the final marking layout. producing a final marking layout, by modifying the initial marking layout using the marking parameters and the lens order data, the final marking layout representing the markings to be present on the ophthalmic lens; characterized in that the step of producing an additional marking layout further comprises the steps of: receiving a semi-finished marking layout representing the markings applied to a semi-finished lens; and producing the additional marking layout by subtracting the semi-finished marking layout from the final marking layout. receiving a semi-finished marking layout representing the markings applied to a semi-finished lens; and producing the additional marking layout by subtracting the semi-finished marking layout from the final marking layout.