Diagnosis
You want to enter document number &V1&.
In Customizing (Document management -> Control data -> Number ranges),number assignment and number range maintenance is defined for eachdocument type.
You want to assign the number &V1& in an external number range, butthis number is not within the external number range defined.

Procedure
Choose a number which is within a defined internal number range for thedocument type.
First check the number ranges defined in Customizing.