You can ask your members for a legal identity number to display on your invoices.
Step 1: Edit the sign-up form
Go to Settings > Member forms > Sign up form. Double-click on Sign up form, or click once, then on the Configure button.
The new field is called Identity number and will be found in the archived fields. Use the restore button to add it to the active fields.
If necessary, rename the field; for example, an Italian studio might call it "Codice Fiscale" while a Spanish studio would call it "CIF". You can also check the box to make this field mandatory.
Note that this field accepts both letters and numbers, and can therefore be used for a variety of legal identifiers.
Save your modification. Upon saving, you will be prompted to customize the layout. Edit it to your liking, then save and close.
If you configure this field to be mandatory, your members will be prompted to provide it the next time they connect to your studio.
Step 2: Edit the modification form
You probably want this field to appear also on the modification form, the one used to edit the information of a member profile.
Go to Settings > Member forms > Modification form.
If the field is mandatory in the sign up form, then it will have been automatically added to the modification form and made editable.
Otherwise, add it by selecting it from the archived fields section, and check or uncheck the box to decide if it can be edited in the modification form.
Save, then customize the layout of the form if necessary.
Step 3: Use this new field in a marketing form
The field Identity number can be added as a question to a Marketing form.
Go to Marketing > Forms. Click on Add a form or edit an existing form.
Click on Add a field. Select Sign up form questions then Identity number.
If you did not make the identifier field mandatory, using a marketing form could be a way to encourage your members to provide it.
Step 4: Results
This identifier will now be displayed on the member's profile and on any newly issued invoice.