How d I reduce the header spacing on an estimate/invoice?

Glad to have you in the Community space today.

Inside QuickBooks Online (QBO), there is an existing invoice or estimate template that you can freely use for your transactions. You can even create your template to have it set to your preference. I'll write down the steps below to get you going. To begin, here's how:

1. Access your QuickBooks Online company.
2. On the top-right corner, click the Gear icon.
3. Choose Custom form styles.
4. If you don't have an existing template, click the New Style button and then select what type of template you'd like to create.
5. Go to Content page, and then click the EDIT LABELS AND WIDTHS.
6. You can also edit the page margins in the Design page.
7. Once everything is ready, click Done.

For further details about the process, see this page: Customise invoices, estimates, and sales receipts in QuickBooks Online.

In addition, I've got you this handy article to help you manage invoice payments inside QBO: Record invoice payments in QuickBooks Online.

It's been a pleasure to have you here today. Feel free to leave a comment below if you need further assistance with this or have any additional QuickBooks-related concerns. I'll make sure to get back to you. Stay safe!