How to set custom Invoice numbers in Odoo
Name your invoice as you want
In this tutorial you are going to learn on how to set Invoice numeration in Odoo. This includes customisation of prefix and adding suffix, changing number of digits and so on. This is a tutorial that will help you to set the numbering rules for entire system. If you just want to change a single invoice by hand you should use this module (don't worry it is free).
First of all, create a backup. It is not really necessary but it is a good practice. If you don't do it it is fine but one day you are going to regret(like most of us).
Admin account will be necessary as you need to Activate the Developer mode in Odoo. Versions 9 and older by clicking on the user in the top right corner, versions 10 and never in the Settings.
Navigate to Sequences menu
You can find it in the:
Settings/Technical/Sequences & Identifiers/Sequences
Search for "Invoice"
"Customer Invoices" view will be displayed. Click and enter it. You can also find any other views in here and change their settings.
You can edit or remove the prefix. Some companies don't want to have INV/year at the beginning. You can also add a suffix. For example some companies are using"-C" for customers and "-S" for suppliers.
Sequence Size field tells how many digits are in the invoice number and step is the incrementation/jump (some companies only want to have even numbers for customers).
As you can see on the photo there is also a table "From - To" - this is the place where you can set the starting invoice number(first invoice number) and the date Odoo will apply it.
There are companies that starts from "0" every quarter or year so if you work in one of those you are set.
There is more
Some additional tips
If you are switching to Odoo from another system you might have to work in both systems for some time. In this period of time, when work is duplicated try to set the Invoice numbers to be the same as in the old system.
Scroll down to see Legend. Odoo has provided some documentation and additional hints under the "From To" table. Read them and test them before you promise your customer/boss the changes.
Secure your system. Make sure that users can't play with invoicing and setting on their own. Even if they don't break the system they might be able to apply some changes that are hard to reverse. Set permissions for users, and try not to create dummy invoices on the live server.