A method to evaluate empirical values of L3 magnetic sub-state photoionisation cross-sections has been reported. Preliminarily, the method requires scanning of the existing experimental data on L X-ray fluorescence (XRF) cross-sections for energy dependence of Lα/ Lℓ cross-section ratio. After assuring the energy dependence of Lα/ Lℓ cross-section ratio, the ratio is used for the determination of the alignment parameter A2. Thus, the determined A2 value, along with the available data on the sub-shell photoionisation cross-sections σ Li and the Coster–Kronig transition probabilities f ij , is used to evaluate magnetic sub-state photoionisation cross-sections σ Li ( m) for m= 3 2 and 1 2 . The method has been used to evaluate L3 magnetic sub-state photoionisation cross-sections for four elements with Z⩾82, from the measured L XRF cross-sections. To the best of our knowledge, until this date neither theoretical nor semi-empirical data on magnetic sub-state photoionisation cross-sections for these elements has been available, for comparison with such cross-section values and to establish the superiority of one data set over the others.