Many sole traders want to invoice professionally without subscribing to Xero or MYOB and paying a larger fee.

From a quick check online, the one that looks best is zoho. It’s mobile app is described at

Cost is $120 for a year for up to 50 customers and a $240 for a year for up to 500 customers.

A quick trial showed that it was easy and intuitive to use. You have to add GST and ensure your currency is set up correctly but once done, it’s quick and easy.

The other ones I looked at were Freshbooks (too expensive), Reckon Invoicing (free but mobile app only, so I didn’t look any further) and Invoicely, which looked ok but didn’t have the sophistication of Zoho (eg. Zoho asked for the ABN when registering and had an easier to upload logo, whilst Invoicely’s logo upload didn’t work for me for some reason).