My old boss told me that one year he was working as an apprentice under the table. Now at the time, a letter for the hours was all you needed. Heck, 1500 of my hours came from a letter from my dad's employer in New Mexico who I worked with for a less than a year.
Anyway, at tax time my old boss's employer gave him a 1099 without warning.
So on one hand, it's your buddy's responsibility if he was working under the table (or at least maybe doing "side jobs" the whole time), but most likely his "employer" didn't want to deal with all the paperwork.
Maybe he could appeal to their common sense and say, "Even if I divided my total gross income over the years by $20 an hour that would still come to 8000 hours." Or work backward and divide his 8 years of income by 8000 hours to come up with an hourly rate and say, "You think I was making $xx per hour?"
For averaging sake let's say he worked 8000 hrs at $10/hr and 8000 hrs at $15/hr over those 8 years. That's $80,000 plus $120,000. That's $200,000 over those 8 years. Divide that $200,000 by 8000 hours and that would mean he was averaging $25 an hour if he truly only worked part-time 8000 hours over the 8 years. Not an incredible amount of pay, but certainly enough to justify that he had worked the required time. If his employer was able to vouch that all of those 1099's were for supervised electrical work that should be enough.
I mean, do they think he was only working 8 hours a week and getting paid $62.50 per hour?
And if they do think he was getting paid that much per hour, perhaps he deserves it because he's that good and who gives a care how many hours he actually worked if he knows what he's doing?