The key word here is 'selling'. Unless you are a certified public accountant, or licensed to do so ... you may be sued for your efforts. The issue is 'selling' your talents. Whether it's a haircut, oil change, or even recommending a stock. You have to be licensed.
Where can I get information about becoming a licensed IRS tax preparer?
You do not have to be licensed or certified by the IRS in order to complete someone's income tax return for pay. You are, however, required to sign the return as a "Paid Preparer."
An income tax return preparer may be subject to a civil penalties for knowingly preparing tax return(s) or refund claim(s) which understate the tax liability or overstate the refund based on unrealistic information. They may also be barred from limited practice for unethical and improper conduct. While not required to examine or review documents or other evidence to independently verify the taxpayer's information, the preparer must make reasonable inquiries if it appears to be incorrect or incomplete, or to determine the existence of required facts and circumstances incident to a deduction. Refer to Reg. 1.6694-1(e)(1).
For additional information, refer to Publication 470, Limited Practice Without Enrollment, Publication 947, Practice Before the IRS and Power of Attorney, and Revenue Procedure 81-38. For information about becoming a Enrolled Agent or taking the Special Enrollment Examination, visit our Director of Practice Enrolled Agent Program page.
By the way, I think my mechanic's also risking arrest, I don't think he's a licensed oil-changer.