The USCIS just released the Visa Bulletin for May 2018.
This bulletin summarizes the availability of immigrant numbers during May for: “Final Action Dates” and “Dates for Filing Applications,” indicating when immigrant visa applicants should be notified to assemble and submit required documentation to the National Visa Center.
A. FINAL ACTION DATES FOR EMPLOYMENT-BASED PREFERENCE CASES
On the chart below, the listing of a date for any class indicates that the class is oversubscribed (see paragraph 1); “C” means current, i.e., numbers are authorized for issuance to all qualified applicants; and “U” means unauthorized, i.e., numbers are not authorized for issuance. (NOTE: Numbers are authorized for issuance only for applicants whose priority date is earlier than the final action date listed below.)
Please check the priority date for your immigration application and submit required documents accordingly.
Cite and refer to https://travel.state.gov/content/travel/en/legal/visa-law0/visa-bulletin/2018/visa-bulletin-for-may-2018.html