We use a software called Receipt Bank which seamlessly integrates with Xero for expense management. The beauty of Receipt Bank is that capturing invoices can be reduced to simply forwarding an email, attachment, or picture to an email address for your own account. So for example, if you have a regular supplier you can simple set up an auto-forwarding rule to automate capturing the invoices for purchasing inventory. For arbitrage sellers, you can use their app to capture expenses by just taking a picture in-app.
We choose Receipt Bank because it currently offers the highest fidelity for reading expenses based on it's machine learning OCR engine, which lets us be a lot more efficient.