Invoice reference &1 &2 &3 does not reference an invoice

What causes this issue?

You post a payment, transfer or down payment clearing with invoice
reference. However, you have chosen a document that is not an invoice.

System Response

So that the <LS>Payment Selection</> program can update payments and
their transfer documents correctly in Funds Management, it requires the
invoice reference on an invoice document.

How to fix this error?

Change the invoice reference and create the reference to an invoice
document.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.