Opinion of Advocate General Kokott delivered on 16 November 2023.#Dyrektor Izby Administracji Skarbowej w Bydgoszczy v B. sp. z o.o., anciennement B. sp.j.#Request for a preliminary ruling from the Naczelny Sąd Administracyjny.#Reference for a preliminary ruling – Taxation – Value added tax (VAT) – Directive 2006/112/EC – Provision of recreational services and services to improve physical fitness – Sale of passes giving access to services whose existence is evidenced by a cash register and by cash register receipts – Taxable amount – Error in the tax rate – Principle of fiscal neutrality – Adjustment of the tax debt as a result of a change in the taxable amount – National practice that does not permit, in the absence of an invoice, a correction of the VAT and a refund of the overpaid VAT – No risk of loss of tax revenue – Plea of unjust enrichment.#Case C-606/22.