Invoice2go is a simple invoicing application available for the iPhone and iPad.

I used Invoice2go for a couple of years running my lawn mowing
business, and was quite pleased with it.

It was a very useful app as a small business owner, and being a one
man show for a lot of the time, it took care of all my needs.

I tried some more advanced software at times, like MYOB or Quicken,
but it felt like learning to fly an aircraft. Invoice2go did my
invoicing, sent reminders to clients who hadn't paid, showed me who
still owed me money, and I could use it from my phone or iPad. This
meant I was able to invoice clients as soon as I had done the job, and
didn't need to come home to a pile of invoicing to do.

It had a few bugs in it over the time I had it, but they were
generally ironed out and the support from the developer was great.
They also brought out a cloud syncing feature so my iPad and iPhone
could sync with each other.

Over all I was very impressed with the app, and felt it was well worth
the price.

5 Stars.