Opinion of Advocate General Collins delivered on 10 March 2022.#Finanzamt B v W AG.#Request for a preliminary ruling from the Bundesfinanzhof.#Reference for a preliminary ruling – Freedom of establishment – Articles 49 and 54 TFEU – Deduction of final losses incurred by a non-resident permanent establishment – State which has waived its power to impose taxes under a double taxation convention – Comparability of situations.#Case C-538/20.