1. Click the gear icon in the top right, then Custom Form Styles under Your Company.
2. Start a new style or edit an existing one. Click New Style and choose Estimate, or click Edit next to a style you already use for estimates.
3. Set the Design tab. Pick a template layout, upload your logo, and set the color scheme and font. This is the look of the whole document, not just the numbers on it.
4. Set the Content tab. This controls what actually shows up: header fields (estimate number, date, expiration date), which columns appear in the line-item table (quantity, rate, amount, a custom column if you need one), and the footer message.
5. Add custom fields if you need them. Under the Content tab, you can add a field for something QuickBooks doesn't track by default, a job site address or a PO number, and choose whether it shows internally only or on the printed estimate too.
6. Preview, then save. Use the preview pane to check the layout before committing. Saving applies the style going forward; it doesn't retroactively change estimates you've already sent.
7. Set it as the default, if you want it to apply automatically. Back on the Custom Form Styles list, use the dropdown next to your new style and choose Make default, so every new estimate uses it without you picking it each time.