Your logo needs to be between 300 x 300 px to 400×400 px – in other words, a perfect square within that range. This is because of the parameters set by payment integrations with Square, PayPal, and others. There are many free online tools to crop your logo to this size. You can always leave your logo blank if you’d like, and your invoices will still work. The video below explains more (starting at about 0:55 in the video):
How Can We Help?