Error at the time of order confirmation in CO11N

Dear Guru's,

I am working on a support project for a manufacturing project.

User facing a problem while confirmation of production order in CO11N. system gives error message as:

"A master record for 100401/PPLAB1 exists only in 2012" for plant.

I want to know the reason behind this error and how to solve this.

Regards,

Saniket