Hello there, @jean6.

Let's open the bill so you can change the reference number on the Pay Bills page in QuickBooks Online (QBO) and manage your expense transactions accordingly.

The Ref No. in the Pay Bills page is the Bill no. info when you create the bill. Then, when you select the Print later option on the said page, the Starting check no. will show as To print. 

Whenever you're ready to change the reference number of your bill, follow these steps:

1. Go to the +New button.
2. Select Pay bills.
3. On the Pay Bills page, select the bill that you want to change the reference number.
4. Once the bill is open, change the reference number in the Bill no. field.
5. Click Save or Save and close.

Once you're done, go back to the Pay Bills page to see the updated reference number and pay your bills. For the complete guide to tracking bills and recording payments in QBO, you can refer to this article: Enter and manage bills and bill payments in QuickBooks Online.

Also, you may want to check out this article as your reference to guide you in paying bills online for a faster transaction in QBO: Pay bills in Online Bill Pay.

If there's anything else you need or questions about managing bills and expense transactions in QBO, I'm always ready to help. Take care, and have a great day, @jean6.