Beware of the google doc scam that is making the rounds. If you receive an email invite to ‘google docs’, it’s not from Google. While it appears to be and indeed uses the google site, it’s a very clever phishing scam. Google are working on a fix but until then, do NOT click on the invite, simply delete it. Further info here https://techcrunch.com/2017/05/03/psa-this-google-doc-scam-is-spreading-fast-and-will-email-everyone-you-know/.
There are loads of this type of phishing scams at the moment. From this is your receipt or invoice to change your password to secure your account. Be alert.