You should get an email shortly after the completion of your trip. There are many other ways you can download or check past invoices.
Within the iOS app
Tap the Account tab > Activity > Click on the trip > Download invoice as PDF
Within the Android app
Tap the side menu > Billing History > Click on the trip > Download invoice as PDF
On the web browser
Log into mevo.co.nz > Activity > Click on the trip > Download invoice as PDF
*within the web view, you can select a date range and download an entire summary.