Every time I make a payment with qb online, the ref no box is prepopulated with some old rubbish. how can i ensure that this box is permanently empty?

Hello Feli, thanks for reaching out to the QuickBooks Community today

The Reference no. is a required field on purchase forms and currently there is no option to edit the default setting. If you would like to submit feedback to our Product team, please select the Settings wheel > Feedback in your account. 

Thanks again for reaching out to Intuit QuickBooks Support on the Community. Have a great day.