Dear PROFESSIONAL,
When it comes to model standing orders as per the Industrial Employment Standing Orders Act under the BIR Act of 1946, there is no need to separately get certified as the act becomes applicable if during the preceding 12 months the strength of workers is more than 100. It does not matter whether the workers' union signs it or not. The standing orders automatically become applicable.
In this matter, you should take into confidence the Labour Officer concerned. He will do the needful.