It is, of course, important that every invoice has an invoice number.
But how do you set this up in MICE?
Step 1: Go to Setup (in the blue menu bar, click on the 'gear' icon at the top right).
Step 2: Select Billing (at the left menu, below settings)
Step 3: Scroll down to the heading 'Invoicing identifier template'
Here you can create your invoice number.
Here is how to fill it in:
(Y) whole year 2020
(y) abbreviated year 20
On the right you will then see the next invoice number.
Note that when you create your first invoice number half way through the year that you start with the number where you left off. As an example when your last invoice number ended at 20;
[y]00021 = 2000021