If you've left a location, but still have the check-in confirmation page open, you will still be able to check out.
However, if you've navigated away from the confirmation page - please visit tracing.co.nz, enter the business' location code (or select the business manually), select 'Check-out' and enter your details. Once that's done, you will be able checked out of the location.
Locations that have not been checked out of for an extended period will be cleared automatically.