As per 7th pay commision recommendation the Non-creamy OBC certificate validity is one financial year . This is how it is calcuated,

(a) Every candidate seeking reservation in central government posts and services as OBC candidate is required to submit a certificate confirming his/her status as OBC and also produce Non-creamy layer status issued by an authority mentioned in DOPT Office Memorandum No.36012/22/93-Est(SCT) dated 15.11.1993.

(b) The Non-creamy Layer Certificate would be applicable to OBC candidates who are covered under Income/Wealth Test criterion. The income limit is decided on the basis of income earned during three previous financial years preceding the year of appointment. To illustrate, the validity of non-creamy layer certificate issued during any month of the financial year 2016-17 covering 3 preceding financial years viz. 2013-14, 2014-15 and 2015-16 be accepted by the concerned authorities for any appointments or recruitments which would be valid during the period April 2016 to March 2017 ( which is that particular financial year)

I would like to add some points:

(i) If Non-creamy certificate required for getting appointed into State Gov or Central Gov. both has different format and validity therefore one need to apply different application for acquiring respective certificate.

(ii) Generally the validity of NCL for Central Gov. is 1 year.

(iii) Whereas Validity of NCL for State Gov. is 3 years.

I hope this helps you,

All the best