What causes this issue?

Posting to company code &V1& is not permitted, because the company code
is flagged as a template.

System Response

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

How to fix this error?

Do either one of the following:
Make sure the document is not posted to this company code.
Remove the template flag from this company code using transaction
<DS:TRAN.FINSC_CO_CD_TEMPLATE>FINSC_CO_CD_TEMPLATE</>. Note that the
customizing for company codes not flagged as templates is subject to
additional constraints. The customizing must be fully consistent to
successfully post documents. Any inconsistencies are reported during the
posting process.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.