Retention amount in the EInvoice XML

Many of our customers have contracts which need accounting for the retention amount in their buisiness transactions.

As per the XML Implementation standard, no XML tag is present for the ‘Retention amount’. Due to this we are currently unable to send the ‘Retained amount’ in the EInvoice.

Our customers are insisting that the Retention amount must be sent in the EInvoice XML correctly exactly as applicable for the transaction.

Let us know how to add information of the ‘retained amount’ in the XML without errors/warnings.