Log in to your Checkbook.io account.
If you have only received a check and not created an account, use this link to set a password to the checkbook account that was automatically created for you with the email that you received the check on.
Go to "Settings" on the bottom left-hand side of the page.
When in 'Settings', click on the "Authorized Users" tab
When in 'Authorized Users', click "Add User"
Add the Full Name and Email Address of the person being added as an Authorized User.
Once the Name and Email have been added, choose "Read Only" or "Read/Write" based on the level of access that you would like to give the user in question.
Access Levels :-
Read-Only: Authorized User can only review your transactions (like an accountant)
Read/Write: Authorized User can create transactions and make payments
Once added, the Authorized User will need to log into their Checkbook account and simply toggle over to your account via the top right drop menu