Start naively and small. (changes made) Start with an explanation without doing research and not enclosing any documents other than the specific items they ask of (if you can get those for free). The explanation would consist of a letter stating that he never visited that outfit, never did work for that outfit, never earned the income, never received the income, etc. You can format the IRS letter the bam bam bam way like
* I never went to that city
* I never applied to that outfit
* I never worked for that outfit
etc.
The IRS should open a case. Their next letter should contain something more that their original computer generated letter and tax bill. If you get merely the same letter from them then you send a copy of your same letter back. Once you get "more information" which means they opened a case manually as opposed to let their computers send out another notice, your step two is to ask the IRS for the name of the source of the "income" supposedly not reported preferably a copy of the actual 1099 form with the name of the recipient/taxpayer.
I would hold off on actually calling the company. YOu can write a simple letter asking for their copy of the 1099. Then another letter stating that DsS did not work for them and they need to send a correction to the IRS. Send the same letter again a little later (don't sit down and compose a new letter) if you don't get a reply. No point spending lots of time and anytime minutes / long distance charges on the phone begging them to do anything because if they balk at correcting the situation, they will string you along.
I say it is safe to not hire a lawyer until after it goes to court and you go there by yourself in person and you lose anyway. And I say you can kibitz DsS all you want or need without being a lawyer yourself.
DsS should feel free to call again to clarify himself or add information or correct himself if he felt he botched up a conversation.
The Social Security Administration sends almost everybody an annual earnings report. If DsS gets a report with extra earnings as well as with missing earnings, then he should send in a dispute letter for that. If DsS does not get a report, to prevent a prolonged period that "his" report goes to some imposter, when you receive your earnings report you should think, "Where's his?" and tell him to inquire of the SSA to find his.
Even though you are dealing with the most powerful collection agency in the world, I think you can get away with missing deadlines while waiting for snail mail in lieu of using express mail and faxes, so long as they know that a dispute is well under way.