How long does it take to get decision on Cap exempt visa filed in prenium processing?

Hello,

I employer falls in one of the category for cap -exempt, so we plan to file my H1-B in non-cap? How long does it typically take to get the decision, if filed using premium processing?

Under premium processing you get the result within 15 calendar days. What so ever be the result you shall know in 15 days irrespective of cap exempt or any other processing.

No, what I meant to ask is, how long does it take for one to know decision on non-cap category for H1-B?

You should get the result within 15 calendar days. If USCIS doubts if the employer really qualifies for cap-exempt category or not, they would issue RFE within that 15 calendar day period.

Whether RFE is issued on 1st day or 15th day, no one can say.