Some of the features I am looking for:
Input your business info, Input client info, Input project details and cost, Generate invoice PDF, Generate receipt PDF,
Bonus:
Ability to mark/track who had paid and outstanding balances.
It's pretty trivial to set up a template, a data source, and have the mail merge feature generate your reports for you. If you F4 in Writer, pick a data source you can drag&drop fields or queries directly into the document where you want them. The rest is just a case of trivial document editing which you're more than likely already familiar with.
Your data source can be anything from a csv (spreadsheet), an .odb or an external data connection to a database (eg, postgres).
(it's a service, not opensource software though - I assume you really meant free or opensource)
great find! thanks!
Their free plan supports invoices for one customer, so you can try it out easily. I'm on the undocumented $10/month plan for 5 customers but was on the $20/month for 25 customer plan for ~2 years.
(I have a regular job right now but have a few projects here and there that come up.)
It is written in PHP and the licence gave me permission to edit it the way I needed, so I did.
The same company also makes a "full-featured" alternative called Duet[1] that costs 49$ to buy.
[0]: http://www.getsoloapp.com/
[1]: https://duetapp.com
For my purposes free doc templates (in my case Google Docs) serve my invoicing purposes perfectly well though. Plain docs are also nice in that they're more flexible than a web based app.
It's abandonware, IIRC, but it's good software.
It's free to install using the community version and some technical knowledge.
Or if it's not at great volume, you could just do it the old fashioned way. About $20 at your local stationary store should sort you out.
However, I think BlinkSale gives you 3 free invoices a month or something like that.