Execution of 2 monetary declarations at same time is not allowed

What causes this issue?

You try to execute two cash declarations at the same time.
The following documents are regarded as cash declarations:
P = periodical declaration
J = annual prepaid declaration
E = final annual declaration
U = partial year declaration

System Response

The declaration cannot be executed.

How to fix this error?

Change the consecutive documents of the main document type of the
recycling partner, since at least one consecutive document is of
type P, J, E or U.

Error message extract from SAP system. Copyright SAP SE.