I am a software developer and as such my productive output is easily repurposed.
A few years ago, long before I was employed at my current job, I made a piece of software in an attempt to persuade a client to upgrade their business processing system. That client didn't buy my software for various reasons unrelated to the quality of the software itself (competitors' bids were all scrapped as well).
Today one of my managers approached me and wanted to see how feasible it would be to make a moderately complicated piece of software - mobile app to collect data in a wizard-like manner and produce printable reports.
There are some gotchas in the project that make it less-than-trivial:
hundreds of data points
reports customizable per client, per region and per user
rules about the points that are needed can change at a whim
... all of which were features of the software I had previously created, along with some tools that help manage the system after it's up and running.
The current situation
It took me some 6 months to create that system and I could deploy it at my current employer's within a couple weeks (modifications/plugins will be needed), instead of the 6+ months it would otherwise take to create it from scratch (longer than my personal effort due to corporate overhead). I have been at my current employer for about 8 months.
I fully own the rights to my previous work. I would like to sell or license the software I've made to my current employer but I'm not sure how to approach that or how to raise the question - I wouldn't want my employer to think I'm holding back on my effort if they decide not develop from scratch in-house. It's also difficult to put a price tag on software and I wouldn't want my management to think I'm trying to rip them off.
How can I approach my current employer about buying my past work?