Hi there, PSElec. 

The option to set 30 days from the end of the month isn't available in QuickBooks Online (QBO). I can see how this functionality would be beneficial to your business. 

I encourage you to add your vote by sending a feature request in the Feedback section within QuickBooks. Our product development team reviews the suggestions they receive to ensure we’re meeting the needs of our customers.

Here's how:
 

1. Select the Gear icon at the top, then Feedback.
   
2. Enter your comments or product suggestions then select Next.
3. You'll be provided a list of suggested Help articles related to your comment. You can read through them or select Skip and send a message.
4. From the drop-down, choose the appropriate category, then select Send a message.

In the meantime, we can create a new payment term and set it to 30 days. I'll show you how:

1. Go to the Gear icon and select All Lists.
2. Click on Terms, then New.
3. Select Due in fixed number of days.
4. Enter 30 days.
5. Click Save.

I've added this article to learn more about payment terms and personalising sales forms in QuickBooks:

• How to Adjust Invoice Payment Terms
• Customise invoices, quotes, and sales receipts

Please let me know if you have any other issues or concerns. I want to make sure everything is taken care of for you. Have a great weekend!