text: Ir 
  
  Pr = Po x ( — ) 
  
  Io 
  where:  Pr = revised price; 
  
  Po = price in the tender; 
  
  Io = index for the month in which the FWC enters into force; 
  
  Ir = index for the month in which the request to revise prices is received. 
  
  **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**
  
  Payments are made in euros, unless another currency is provided for in Article I.7. 
  
  **II.21.3. Conversion**
  
  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 