Overall budget exceeded by &2 for document item &1

What causes this issue?

The overall budget is exceeded by &V2& for the document item &V1&.
Budget control raised this message for the following combination of
availability control ledger and control object:
&V3&&V4&
Note: The control object is defined for a grant/fund/sponsored
program/sponsored class/budget time slice.

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?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.