In this day and age shares issued for services are restricted but can use the 144 holding period exemption to become free trading. That means holding six months for an SEC filer.
What the issue usually is for removal of the restrictive legend is determining when they were “fully paid for”. That is usually when the work is completed even if the shares were issued prior to that.
There is a paper trail just as there is a trail for shares issued to employees, there is a legal document created detailing the price the shares were issued, for what amount issued and what the vesting requirements are.