Thanks for the clarification, alex.heath.light.

I cannot tell the specific size pixel by pixel of the logo. Though QuickBooks recommends using square-shaped. Other than that, the system will not allow the logo to use in QuickBooks.

Aside from sizes, below are recommended when adding a logo to sales forms in QuickBooks Online. It's all based on our articles that guide you on how to input a logo in your book. Here are the lists:
 

• a .gif, .bmp, .png, .jpg, .jpe, or .jpeg file
• smaller than 10 MB
• 24-bits or less in bit depth (or colour depth)
• using the standard RGB colour spaceNote: If your logo is CMKY-formatted, convert it into an RGB image using tools (such as Adobe Photoshop) before you upload it to QuickBooks Online.

Please let me know if you have other questions about managing the logo in QuickBooks Online (QBO). Take care! Thanks!