Google announced on Google+ that they are going to be expanding their GTINs (Global Trade Identification Numbers) requirements for the Google Merchant Shopping feeds.
In September 2015 Google began requiring GTINs for many products from a list of 50 brands. Now, Google is expanding that requirement for any merchant "targeting the US, Australia, Brazil, the Czech Republic, France, Germany, Italy, Japan, the Netherlands, Spain, Switzerland, and the UK to submit correct GTINs and the corresponding brand for all new products with GTINs assigned by the manufacturers."
Providing GTINs is vital to ensuring that Google recognizes your products and can offer the best experience possible for consumers. We’ve seen that including GTINs can unlock performance improvements that may directly benefit your advertising efforts. In fact, offers matched to the Google Shopping product catalog may receive up to 40% more clicks than unmatched offers.
So make sure you are compliant and to learn more, see this help page.
Forum discussion at Google+.