For those of us who work in the design and programming of freelancers, A very important part is presenting the client with a detailed invoice at the end of the job, and if we can do it in what we do best (HTML), then better than better.
From CSSTricks they propose us one that they have designed and that it can be luxurious, simple but leaving all the points clear and without fanfare that are not necessary in something of this type. I quite liked it.
You can keep an eye on it, see a demo and even print it from CSSTricks.