Difference between InstdAmt and EqvtAmt

ISO 20022 specifies two methods to present the order amount in payment messages. InstdAmt and EqvtAmt, as shown below in an excerpt from schema:

The definitions for these are:

InstructedAmount   <InstdAmt>
Amount of money to be moved between the debtor and creditor, before deduction of charges, expressed in the currency as ordered by the initiating party.

EquivalentAmount   <EqvtAmt>
Amount of money to be moved between the debtor and creditor, expressed in the currency of the debtor's account, and the currency in which the amount is to be moved.

In other words, EqvtAmt is used when order is done with a different currency than the one in Debtor's account. SEPA payments, for example, normally always use InstdAmt.

XML examples:

<Amt>
   <InstdAmt Ccy="EUR">100</InstdAmt>
</Amt>

<Amt>
   <EqvtAmt>
      <Amt Ccy="EUR">100</Amt>
      <CcyOfTrf>USD</CcyOfTrf>
   </EqvtAmt>
</Amt>