The federal entry requirement is one number. The IRS states it directly: "Any tax professional with an IRS preparer tax identification number (PTIN) is authorized to prepare federal tax returns." There is no federal examination, no federal education requirement and no federal license for preparers generally. Some states impose their own requirements on preparers operating there, but at the federal level the credential landscape is voluntary above the PTIN.
The Annual Filing Season Program is the voluntary tier, and the IRS says so in as many words. Asked whether the program is mandatory, the IRS answers: "No, it's voluntary. Anyone with a preparer tax identification number (PTIN) can prepare tax returns for compensation." A participant completes 18 hours of continuing education including a six-hour federal tax law refresher course with a test, renews their PTIN, and consents to the practice obligations in Circular 230, Subpart B and section 10.51. Someone who has passed certain recognized tests takes a reduced 15 hours. Completing it produces a Record of Completion, not a license.
Representation rights are where the tiers actually bite, and they matter most at the worst moment. The IRS divides preparers into three groups. Enrolled agents, certified public accountants and attorneys have unlimited representation rights and "may represent their clients on any matters including audits, payment/collection issues, and appeals." Annual Filing Season Program participants have limited representation rights: they "can represent clients whose returns they prepared and signed, but only before revenue agents, customer service representatives, and similar IRS employees, including the Taxpayer Advocate Service." A preparer who holds a PTIN and nothing else has none at all; for returns prepared after December 31, 2015 the IRS says such preparers "will only be permitted to prepare tax returns" and "will not be allowed to represent clients before the IRS." The consequence is concrete: if the return is examined two years later, the person who prepared it may be unable to speak to the IRS about it.
The signature is the checkable safeguard. A paid preparer is required by regulation to sign the return and to furnish an identifying number on it. Section 6695, headed "Other assessable penalties with respect to the preparation of tax returns for other persons," imposes a penalty at subsection (b) for failing to sign and at subsection (c) for failing to furnish the identifying number. A preparer who charges a fee, prepares the return, and then leaves the preparer section blank has not made an administrative slip; they have avoided the one record that ties them to the document. The IRS publishes a searchable Directory of Federal Tax Return Preparers listing attorneys, certified public accountants, enrolled agents, enrolled retirement plan agents and enrolled actuaries with valid identifying numbers, along with Annual Filing Season Program participants, which is the practical way to check a name before handing over documents.
The routes available, from most to least self-directed. Commercial tax software puts the work on the filer with the software supplying the rules. IRS Free File offers guided software at no cost through IRS.gov to filers under an annual income limit, and Free File Fillable Forms offers electronic forms with no income limit and no guidance. Volunteer programs provide in-person help free of charge to people who qualify. And a paid preparer, at any of the three credential tiers above, does the work for a fee. Whichever route is used, the taxpayer signs the return under penalties of perjury and remains responsible for what it says.