SOLAS Verified Gross mass: For anyone who imports or exports using containers.
From the 1st July 2016, the shipper of products by sea in a container is responsible for providing the container's gross verified weight to the ocean carrier and port terminal representatives prior to it being loaded onboard vessel. The vessel and terminal operator are required to use verified container weights for vessel stowage planning and are not allowed to load a packed container aboard a vessel for export if they do not have the Verified Gross Weight (VGM).
In November 2014, the International Maritime Organization (IMO) adopted mandatory amendments to the international convention for the Safety of Life at Sea (SOLAS) Chapter VI, Part A Regulation 2 - Cargo information which is applicable globally.
A good summary of the reqirements can be found on the world shipping site. (Link to the website is below)
Your Freight Forwarder may also be able to provide information about how they are implementing this new regulation.