In Moloni, it is possible to set a default document series for a customer.
With this functionality, whenever you add a customer to a document, the series you have defined is automatically selected.
Follow these steps:
1. Go to the Contacts > Customers menu.
2. Then, search for the desired customer and click on them.
3. Next, select the Billing tab.
4. Here you will find the Document Set field, choose the series you want to associate with this customer.
5. To save the information, click Save.
From now on, whenever you create a document for that customer, the default series you have set will be automatically associated.