We can manually create a Business License field and add it to your invoices since we don't have the option to tap a button to place it in the invoice form. Let me be your best help in performing this.
Through a custom field, add a Business License section to the invoice form. Then, show it to your printed invoice or whenever you send it to your customers. Here's how:
Go to Settings.
Below the Lists column, select Custom fields.
In the upper right corner, click the Add field.
Name it Business License or anything you want. Tick the box All Sales forms, you can also include Purchase Order. Then, turn on Print on the form beside it.
Once done, tap Save. It will now show on your invoice form.