14.4. Contract liabilities

Approximately PLN 471 million of the contract liabilities balance as at 1 January 2020 was recognised as revenue in the 12 months ended 31 December 2020. Approximately PLN 460 million of the contract liabilities balance as at 1 January 2019 was recognised as revenue in the 12 months ended 31 December 2019.

In 2018, the Company and T-Mobile Polska signed a long term contract on telecommunications access to Orange Polska’s fiber network in the form of Bitstream Access. OPL S.A. started providing services in December 2018. The fees under the contract comprise mainly a fixed upfront fee of PLN 275 million, a fixed fee for infrastructure set-up, IT systems integration and monthly fees for each customer. The revenue from the contract is recognised during 15 years which currently is the estimated period of the contract. The Group applies input method to measure revenue for the period with the application of constraint in respect to recognition of revenue to the level that is highly probable not to be reversed in the future. As a result, the fixed fee elements will be evenly accounted as revenue over 15 years, while the variable fees dependent on the number of end-customers will be recognised as revenue based on the actual number of customers in the period.