InvoiceOwl – Send and manage beautiful invoices

For example, blog posts, sign-up pages, and fundraisers can't be tried out, so they don't count as Show HNs.

When the project is software, you have to have something people can just try out, either by going to a website or downloading an app. It's great that you have working software—that's much better than just collecting email addresses for later—but it still needs to be publicly accessible in order to count as a Show HN.