XML Check File (ISO20022) - Incorrect Check Number

Summary

XML Check File (ISO20022) - Incorrect Check Number being generated

Content

I am generating an ISO20022 xml file and transmitting the output to the bank to process and print checks.  I have the following xml tag in the program that generates the output for the check number:

<ChqNb>
          <xsl:value-of select="/OutboundPaymentInstruction/OutboundPayment/PaymentNumber/CheckNumber"/>
 </ChqNb>

However the ChqNb value picks up the first value  appearing as the "Paper Document Number on the payment file and assigns the same number for each transaction in the file.  In other words all transactions across multiple suppliers  in the file have the same check number.