Hello Leicesterlifecoa,
Thank you for joining us on the UK Community Page for QuickBooks.
If you are wanting to do the accounts on our QuickBooks Self Employed Product, you'd just need to log-in and log out of each account on the device in question as you need to swap between the two, entering your email for yours, and your husbands for your husbands.
However, if you are doing the accounts on our Online Product (Simple Start, Essentials or Plus) - you will have the facility to use the "Switch Company" facility, and access both through on email address, added as a user on both business files.