Write Access is the checkbox on Employee card, Secure Web tab, that enables changes. Without this checkbox their connected iPad/iPhone cannot change data in Big Business.
This checkbox has been renamed to be different from the All Access on the Access tab.
In the picture, the paired iPad is set to appear In Print Options and have Write Access. This puts the name "Admin iPad" in Print Options for sending new entries to the iPad. Write Access allows edits made on iPad, such as adding Items, to save to Big Business.