# DCC Calculations

This section describes the process that should be used when calculating the dynamic currency conversion.

### Exchange Rate Calculation

The Base Exchange Rates held on the Authorisation Host are truncated at the 6th minor decimal place. The mark up agreed with the merchant is added into the base rate and then the marked-up rate is, once again, truncated at the 6th minor decimal place. If there is a minor 7th decimal place it is truncated, no rounding takes place.

Example:
Base Rate GBP to EUR = 0.725800
Merchant Mark-up = 3.25%

 Final Rate = 0.725800 + (0.725800 x 3.250000 / 100) = 0.725800 + 0.0235885= 0.7493885 (Rate is truncated) = 0.749388

### Transaction Amount Calculation

The process used for calculating the DCC transaction amount is as follows:

The final amount in the merchant’s pricing currency is converted using the marked-up exchange rate. The amount is then rounded to two decimal places.

The amount is rounded up if the 3rd minor unit is a value of 5 or above, it is rounded down if the 3rd minor unit is a value of 4 or below.

Example 1: Rounding up,

 Merchant Pricing Currency: FX Rate: Transaction Amount (Pre Rounding) Transaction Amount (Post Rounding) €150.000 0.749388 £112.408 £112.410

Example 2: Rounding up,

 Merchant Pricing Currency: FX Rate: Transaction Amount (Pre Rounding) Transaction Amount (Post Rounding) €400.000 0.749388 £299.755 £299.760

Example 3: Rounding down,

 Merchant Pricing Currency: FX Rate: Transaction Amount (Pre Rounding) Transaction Amount (Post Rounding) €140.000 0.749388 £104.914 £104.910

Notes:

1. The only exception to the above is solutions using the Elavon POS V2, Elavon POS V3 and Polish ISO 8583 protocols where the amount is rounded to zero decimal places for currencies (e.g. JPY) with a zero minor decimal place exponent. See appropriate authorisation specifications for additional detail.
2. The amount sent in the authorisation must match the amount provided in the settlement records. If there is a discrepancy in the authorisation and clearing amounts the merchant would be subject to integrity fees.