Contract number:  Service contract conditions of December 2018 At the anniversary date, the contracting authority must communicate the final index for the  month in which the request was received, or failing that, the last provisional index 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:  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.  Ir  Pr = Po x ( — )  Io  II.21. PAYMENTS AND GUARANTEES  II.21.1. Date of payment  The date of payment is deemed to be the date on which the contracting authority's account is  debited.  II.21.2. Currency  II.21.3. Conversion  II.21.4. Costs of transfer  Payments are made in euros, unless another currency is provided for in Article I.7. 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 costs of receipt charged by its bank;  (c) the party causing repetition of the transfer bears the costs for repeated transfer.  35 