Error converting sales tax code &

What causes this issue?

An exception occurred in the conversion module for sales tax codes
(POS_CUST_TAXES_CONVERT). The conversion rule for tax code &V1& is
probably not known.

System Response

The record cannot be prepared for POS outbound.

How to fix this error?

<DS:SIMG.W_DF_VK_0127.SIMG_OPOS>Define the conversion rule for tax code
&V1&.</>

Error message extract from SAP system. Copyright SAP SE.