Application PMP

Do you have 12months to write the exam.

I think you are asking the validity period of your application / exam eligibility period.

You have 1 year from the date your application was approved to take your exam. For example, if your application was approved on 5/3/13 then you can take your exam anytime untill 5/3/14.  

You can find more details in the PMP Handbook in  Examination Eligibility section.