Contract number: [ complete ]  Contract conditions of December 2015  available for that month. The contractor establishes the new price on this basis and  communicates it as soon as possible to the contracting authority for verification. The price revision is calculated using the following formula:  Ir  Pr = Po x ( — )  Io  where:  Pr = revised price;  Po = price in the tender;  Io = index for the month in which the contract enters into force;  Ir = index for the month in which the request to revise prices is received.  II.20. PAYMENTS AND GUARANTIES  II.20.1. Date of payment  Payments are deemed to be effected on the date when they are debited to the contracting  authority’s account.  Payments are made in euros or in the currency provided for in Article I.7. II.20.2. Currency  II.20.3. Conversion  II.20.4. Costs of transfer  II.20.5. Pre-financing, performance and money retention guarantees  The contracting authority makes any conversion between the euro and another currency at  the daily euro exchange rate published in the Official Journal of the European Union, or  failing that, at the monthly accounting exchange rate, as established by the European  Commission and published on the website indicated below, applicable on the day when it  issues the payment order. The contractor makes any conversion between the euro and another currency at the  monthly accounting exchange rate, established by the Commission and published on the  website indicated below, applicable on the date of the invoice.  http://ec.europa.eu/budget/contracts_grants/info_contracts/inforeuro/inforeuro_en.cfm The costs of the transfer are borne as follows:  (a) the contracting authority bears the costs of dispatch charged by its bank,  (b) the contractor bears the cost of receipt charged by its bank,  (c) the party causing repetition of the transfer bears the costs for repeated transfer.  28 