G/L account & & does not exist

What causes this issue?

A line item is to be posted to the non-existant G/L account &V1&
in company code &V2&.

System Response

The invalid account number is rejected.

How to fix this error?

If you have entered the account number, correct your entry.
If the account number was rejected when the system created automatic
postings, check which postings it may concern by means of the
business transaction. Contact the system administrator to correct the
account determination for the affected transaction.

Error message extract from SAP system. Copyright SAP SE.