Rules on the entry in the accounts of admission rights. The entry into force of the Kyoto Protocol has led to the entry into force of the Kyoto Protocol. operation of so-called flexibility mechanisms, including the market for emission allowances for effect gases glasshouse. At European Union level, the market begins on 1 January 2005, affecting some 12.000 installations. CO2 emitters. The particular characteristics of the emission market require accounting rules that are consistent with its unique operational nature; and harmonise the practices to be applied by the various countries concerned. This issue, which is not free of controversy, has led to an important issue. discussion on the international scene. In our country, last February, the Institute for Accounting and Audit of Accounts (ICAC) it publishes a rule governing the accounting treatment to be followed by Spanish companies.