tax preparer under 18 years of age
You pose 3 questions, but as another poster noted it's not clear whether you're referring the minor filing his own tax return or preparing a customer's return for pay as an employee of a tax store. If you mean the former, the answers are:
1. No. A working minor (at least one over 13 as of Jan. 1 of the tax year at issue) must file a return and pay tax. Also, it seems there's no reason that he can't sign the return himself; therefore he's required to sign also. In short, he's got the same duties as any other taxpayer.
2. Any employer (it's irrelevant that here it's a tax return store) need only mail a W-2 to the minor and the IRS by Jan. 31 of the following year. If that's done, the employer incurs no federal tax penalty. ( Don't ask me about possible child labor laws!)
3. Goes nowhere.
However, I think you intended to refer to the second scenario. In that case the answers are:
1. and 2. The IRS regs on preparers penalize misconduct and lapses in record-keeping; I've never seen an age requirement but if there is one lurking in some obscure pronouncement, I'd bet a lot that it's an exceedingly minor infraction, with small if any penalties, and that no one cares about, including the Service. As long as the kid signed the return as a paid preparer and entered his correct ID number (and the tax store keeps copies for 3 years, etc.), no one's getting penalized.
3. Unless the customer-taxpayer can show that the kid botched the return AND that any such mistakes cost him money or otherwise actually, he hasn't been "damaged" even if there was an intentional misrepresentation. So there's no case against the kid or his employer.