Welcome to the Community, A Black Towing.

Setting up invoice terms to due every 30 days end of the month can be done by going to the Company settings. Here's how:

1. In your QuickBooks Online (QBO), go to the Gear icon at the top right to get to the Account and Settings.
2. Click the Sales menu at the left pane, then tick the Sales form content section.
3. In the Preferred invoice terms drop-down, choose Add new.
4. Enter a name and select the Due by certain day of the month radio button, then enter 30 in the day of month box.
5. Hit Save to complete the process.

For additional information, consider checking out this article: How to Adjust Invoice Payment Terms in QuickBooks Online.

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!