Budgeting not allowed for commitment item &1/&2

What causes this issue?

Budgeting is not allowed for the commitment item &V1&/&V2&.
The commitment item specified must fulfill the following conditions :
<DS:GLOS.financial_transaction>financial transaction</> must equal 30
<DS:GLOS.item_category>item category</> must equal 2 (for a revenue
item) or 3 (for an expenditure item).
The item should not be a statistical item.

System Response

Process terminated.

How to fix this error?

Enter a commitment item with financial transaction 30, item category 2
or 3, and make sure the indicator for statistical items is not
checkmarked.

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.