I'm not sure what you are asking
Typically you invoice for a deposit using a service type item, and that posts to a liability account (refundable deposit)
then you invoice for the total, and as the last line you use the deposit item, set the qty to negative one, and enter the deposit amount in the rate block
the customer pays the balance
This is not the answer I am looking for. I need my front end entry to always be 35 % of whatever the total invoice is. Not asking how to show the negative in system asking how to make that transaction set to self math itself. If that makes any sense. I know how to take a frontend deposit and put it in the invoice.
QuickBooks Online is unable to automatically calculate the front end entry to be always 35%. You'll have to calculate it manually.
I also got you article about retainers: How to record a retainer or deposit.
In case you have other concerns, don't hesitate to let us know.