• Coversion rates shal not be rounded or truncated when making conversions
• Conversion rates shall be used for conversion in either direction. Inverse rates shall not be used.
• Monetary amounts to be paid or accounted for when rounding takes place after conversion into euro units shall be rounded up or down to the nearest cent.
• Monetary amounts to be paid or accounted for which are converted into a national currency unit shall be rounded up or down to the nearest sub-unit or, in absence of a sub-unit, to the nearest unit.

If the euro cent, in real terms, represent a greater value than either the smallest sub-unit or unit of a national currency, if no sub-unit exists, then in a national currency-euro-national currency conversion rounding errors are unavoidable.