Taxpayers have the right to retain an authorized representative of their choice to represent them in their dealings with the IRS. Taxpayers have the right to be told that if they cannot afford to hire a representative they may be eligible for assistance from a Low Income Taxpayer Clinic.
If you have won your case in court, under certain conditions, you may be entitled to recover certain reasonable administrative and litigation costs related to your dispute with the IRS. IRC § 7430
In most situations the IRS must suspend an interview if you request to consult with a representative, such as an attorney, CPA, or enrolled agent. IRC § 7521(b)(2)
You may select a person, such as an attorney, CPA, or enrolled agent to represent you in an interview with the IRS. The IRS cannot require that you attend with your representative, unless it formally summons you to appear. IRC § 7521(c)
If you are an individual taxpayer eligible for Low Income Taxpayer Clinic (LITC) assistance (generally your income must be at or below 250 percent of the federal poverty level), you may ask an LITC to represent you (for free or a minimal fee) in your tax dispute before the IRS or federal court. IRC § 7526
For more information, see Publication 4134, Low Income Taxpayer Clinic List.