Update in operand &1 not permitted

What causes this issue?

You use operand &v1& as an output operand for a variant. You cannot use
the operand for updating, for one of the following reasons:
The <DS:DE.REG_OPERAND>register operand</> field is selected for the
operand.
If you want to update the operand within the schema:
Register operands are provided internally with the consumption or
demand values of the allocated registers. It is therefore not possible
to update to these operands.
If you want to update the operand to the installation facts:
The operand has operand category DEMAND. Demand register operands may
not be supplied in the installation facts.
The field <LS> Operand for <DS:DE.ALLHISTORY>historical values</> bill
printout</> is selected for the operand.
Variants that use input operand &v1& exclusively, process operand
values from the installation facts. The update to these operands is
therefore not applicable.

System Response

The rate is inconsistent and cannot be saved.
The billing of the inconsistent rate is terminated.

How to fix this error?

Choose another output operand in the rate.
Correct the rate in billing.

Error message extract from SAP system. Copyright SAP SE.