If your client is already using Receipt Bank independently, they can easily ‘Grant access’ to you from the ‘Account details’ tab under their ‘Account settings’ menu. They’ll find the ‘Grant access’ button there, which needs to be hit and your details added.
Then an invitation will be sent to you. Once you accept it, the client will be added to your account and you can take on their subscription.
This will transfer all of their items, chart of accounts, suppliers list and other information to your account, where you can easily access and edit them.