What’s the lowest permission level to externally share a document from SharePoint Online?

Hi All,

We have some document libraries on our Sharepoint online platform which our office teams use. We have it locked down so that they can read/write the documents but not edit permissions, change page content etc. Basically they can only read write the documents, that’s it.

We have now found that this prevents users sharing documents with external people with the only share option available being to share with those that already have permissions. 

Whats the lowest level permission needed to resolve this whilst also restricting access to amending permissions manually or editing lists/views etc.

Thanks all.