Ask HN: Where can I find an example of a professional functional specification?

Hmm. I've never seen a requirements document for a 6-figure contract.

I have seen some for low 5-figure ones though.

One starting point could be the IEEE standards (IEEE 830 and 1233)

http://en.wikipedia.org/wiki/Software_requirements_specifica...

http://www.math.uaa.alaska.edu/~afkjm/cs401/IEEE830.pdf

although it's old and superseded

http://programmers.stackexchange.com/questions/159274/what-s...

According to Stack Overflow

"29148:2011 standard seems to replace the IEEE 830:1998."

There are also plenty of books on requirements, like for example:

Mastering the Requirements Process Second Edition by Suzanne Robertson, James Robertson (published by Addison Wesley Professional )

Edit: hopefully there are people here on HN that routinely either write or receive requirements documents of that magnitude and can help you more than I do :)

I've handled my fair share of large scale functional specs (not as a freelancer though) and I've gone through the process of drafting a 6 figure SOW before. I don't have any examples to give you but if you'd like some feedback/guidance I can potentially help. Feel free to contact me (email in profile) if you're interesting.