Tell me what suck about invoicing - suggestions for invoicing app

Hi Makers, - What are the biggest pain points/issues you are experiencing as a freelancer/maker regarding invoicing and payments? - What features would you need to have in an invoicing app? - What features would you like to have in an invoicing app? Bit of a context I am working for a mobile and web invoicing app for small businesses. We are now planning to focus on freelancers and prepare features to solve some of the problems, but I need to identify them first. I am hoping to gather as much feedback and suggestions from freelancers as possible that is why I post it here.