To operate your business, you have to buy things from vendors. The supplier and vendors send the invoice that you have to manage for accurate record management. Not maintaining these bills accurately can cause extra fee, late payments, etc.
Reference: How to successfully start your journey to writing a book or ebook publication. Get published in the literary world! Writing an ebook can be a great way to share your knowledge and expertise with the world. It can also be a profitable venture, if you market and sell your ebook effectively.