Google regularly changes its feed specification requirements to enhance search ability of products in Google Shopping. Google announced several updates to the Google Shopping Feed Specification with the aim being of creating a richer experience for customers to improve their shopping experience. Google is trying to achieve this by updating the Google Policy Shopping Center. Google has changed the structure of the broad areas they covered for Feed Specification as instead of having 6 principle policies they have been reduced it to four broad areas that are:
Prohibited Content - Content you’re not allowed to promote on the Google Network
Prohibited Practices - Things you can’t do if you want to advertise with us
Restricted Content - Content you can advertise, but with limitations
Editorial and technical - Quality standards for your ads and website 
Most retailers won’t be affected by these changes, as Google hasn’t drastically changed too much. Though Google suggests reading through the updated version to be sure to check that you’re in compliance with them as failure to do so shall result in your ads being blocked. These changes have been made by Google in hopes of streamlining their Shopping policies by making them more user friendly and accessible for both users and advertisers. Google have even stated the four main outcomes they expect from these changes are:
Fewer and simpler shopping policies
More transparency into why each policy has been put in place
More insight into how each policy has been put in place
Policies will be aligned across Google’s advertising products 
Perhaps the biggest change announced by Google is regarding the Global Trade Item Number (GTIN) attributes. Google has stated that brands must have both a brand and GTIN attribute in order for them to remain approved within a merchant feed. This is beneficial for retailers as when applied to your products you are making your items even more unique, allowing them to be easily identified within the global marketplace. The addition of GTIN for each product also helps Google in making your adverts richer and easier to find. This is because GTINs help Google in understanding exactly what it is that you’re selling. Getting an understanding in turn helps Google boost your ad performance by adding valuable details about the product and serving the advert in more relevant ways to the user. This also means that your ads can serve in more places on Google, YouTube, and our partner sites. Merchants who've added correct GTINs to their product data have seen conversion rates increase up to 20%. 
Certain items shall not have a GTIN as they could be non-visual branded handmade or made to order products. If this is the case, then such a product you should set the ‘identifier exists’ option to ‘False’. Any item without a GTIN attribute or an identifier set as false shall be removed from the feed entirely, meaning that said product will no longer be visible to consumers within your Google Shopping campaigns.
In addition, it has become mandatory from February 2016 to have a ‘Returns and Refunds’ section on your site that shows to the customers exactly how to return their order. Another change being that it is now a requirement to have a secure checkout that uses SSL even if you use a third party payment provider to handle all credit card data. Google has done this to make retailers more responsible and encrypt all personal information by using SSL when communicating with the server.
It is encouraged that one review’s these new feed specifications as some of the updates may require changes to a current product data feed. To deliver the best online shopping experience you should always make sure to comply with Google shopping policies and to avoid any product or feed disapprovals.