I live in New York. I'm currently employed with a software company and before starting my employment I signed a contract with the company which stated that any intellectual property that subsists or may subsist during employment would be transferred to them. I created my own software application which I created prior to joining the company but for which I added some new features during employment. I plan to leave this company and sell this software under my own company. I don't plan on copyrighting the software. Does my current employer still have a case to say that this software belongs to them even though it's not copyrighted and I don't plan on doing so?
Yes. Your employer has a case to say that the copyrights in the software belongs to the employer, if you worked on the software on company time using company resources.
Was creating software part of your employment duties?
Copyrights exist in a work as soon as the work is fixed in tangible form (e.g., pen to paper, paint to canvas). The copyright is automatic.
Registration with the US Copyright Office is not required for a work to have copyright protection but copyright registration provides the work with additional protection. Not only does copyright registration provide a date of creation and a (rebuttable) presumption of copyright ownership, the holder of a registered copyright also becomes eligible for statutory damages if the work is infringed ($750-$150,000/work).
The holder of an unregistered copyright must register their copyright prior to filing an infringement lawsuit and then will be limited to collecting damages for demonstrable losses/infringer’s profits. No statutory damages.
You should have your employment contract, that transfers rights in the work to your employer, personally reviewed by an IP attorney in your area.