Hello there, Arnorton. You can modify the invoice terms from your account's settings to specify a due date without using default options. Let me guide you through the detailed process.
In QuickBooks Online, establishing flexible variable terms allows you to define the duration you grant your customers to pay for your products or services. Doing so will help them ensure timely settlement.
You can refer to these steps to modify them:
- Go to the Gear icon and select Account and Settings.
- From the Sales tab, locate the Sales form content and click on the pencil icon.
- In the Preferred Invoice Terms dropdown, click on the +Add new option.
- Then, create a term to reflect on the invoice.

Additionally, you'll want to seek additional guidance from our Live Expert Assisted team to help you with customer sales invoice and provide assistance in keeping track of your overall transactions.
Moreover, I'll include this reference to help you review customer-paid invoices in your file: Record invoice payments in QuickBooks Online.
With the information given, you'll able to manage customer invoices and their payments. If there are any further queries, I'm always available to assist you. Keep safe.