United States: Your responsibility

An adviser can prepare the figures, write the technical case and complete Form 6765, and a paid preparer signs the return and gives their PTIN.1Source 1IRS, PTIN requirements for tax return preparers (16 October 2025); 26 CFR 1.6109-2; 26 CFR 1.6695-1(b). None of that moves the return out of the company's name. The research credit is claimed on the company's own federal income tax return, with Form 6765 attached, and the company answers to the IRS for what the return says.2Source 2IRS, Form 6765 (Rev. December 2024), "Attach to your tax return"; Instructions for Form 6765 (Rev. December 2025); the definition of qualified research is in 26 U.S.C. 41(d). The questions on who signs the claim and can we see the full claim before filing? are about making that responsibility real. The people who did the work read the technical descriptions before the return goes in, and the company keeps a copy of what was filed.

• Claiming for a past year. A claim for credit or refund must be filed within three years from the time the return was filed, or two years from the time the tax was paid, whichever is later.3Source 326 U.S.C. 6511(a). An amended corporate return is made on Form 1120-X, only after the original return has been filed.4Source 4IRS, Instructions for Form 1120-X (Rev. December 2025): "File Form 1120-X only after the corporation has filed its original return"; generally within 3 years after the original return was filed or 2 years after the tax was paid, whichever is later. An unsolicited offer to claim for earlier years is worth testing against these dates; the cold calls page says how.
• How long the IRS has. Tax is generally assessed within three years after the return was filed. The period is six years where more than 25% of gross income was omitted. There is no limit for a false or fraudulent return filed with intent to evade tax, or where no return was filed.5Source 526 U.S.C. 6501(a), (c)(1), (c)(3) and (e)(1) (United States Code, 2024 edition). A review can therefore arrive well after the credit has been received and spent, which is why review support in the engagement letter matters (is review support included?).

If an examination reduces the credit, your company pays the difference. Interest on an underpayment runs from the due date until it is paid, and is not removed for reasonable cause.6Source 6IRS, Interest (26 April 2026). An accuracy-related penalty of 20% of the underpayment can apply, and a separate penalty of 20% of the excessive amount applies to an erroneous claim for refund or credit.7Source 7IRS, Accuracy-related penalty (6 May 2026) and Erroneous claim for refund or credit (30 July 2026), 26 U.S.C. 6676. Whether the adviser's fee comes down too depends on the engagement letter, not on the IRS: see what happens to the fee if the claim is reduced?

The preparer can face penalties of their own. A preparer who understates tax through an unreasonable position, or wilful or reckless conduct, faces a penalty under section 6694, and a person who aids or abets an understatement faces one under section 6701.8Source 8IRS, Tax preparer penalties (21 September 2026): 26 U.S.C. 6694 and 6701. Those penalties are the preparer's; they do not pay the company's tax, interest or penalty, and the engagement letter's liability and indemnity clause is where any contribution from the adviser would be found.

If the company finds that a claim was too high, Form 1120-X is the route for correcting a corporate return, generally within three years after the original return was filed or two years after the tax was paid, whichever is later.4Source 4IRS, Instructions for Form 1120-X (Rev. December 2025): "File Form 1120-X only after the corporation has filed its original return"; generally within 3 years after the original return was filed or 2 years after the tax was paid, whichever is later. Take advice before you file it: the correcting a claim page sets out what to settle first, including what the engagement letter says about the fee on the corrected amount.

If the IRS examines the return within the assessment period, it can ask for the records behind the credit. Keep the return as filed, Form 6765 and its calculations, the technical descriptions, the time and cost records they rest on, and the engagement letter. Ask for anything the adviser holds that you do not (ownership of records and work).

• If your claim is reviewed and complaints about an adviser in the United States
• Claim reduced on review and if you are charged a penalty
• The true cost of a claim

Sources

1. IRS, PTIN requirements for tax return preparers (16 October 2025); 26 CFR 1.6109-2; 26 CFR 1.6695-1(b).  Back
2. IRS, Form 6765 (Rev. December 2024), "Attach to your tax return"; Instructions for Form 6765 (Rev. December 2025); the definition of qualified research is in 26 U.S.C. 41(d).  Back
3. 26 U.S.C. 6511(a).  Back
4. IRS, Instructions for Form 1120-X (Rev. December 2025): "File Form 1120-X only after the corporation has filed its original return"; generally within 3 years after the original return was filed or 2 years after the tax was paid, whichever is later.   Back
5. 26 U.S.C. 6501(a), (c)(1), (c)(3) and (e)(1) (United States Code, 2024 edition).  Back
6. IRS, Interest (26 April 2026).  Back
7. IRS, Accuracy-related penalty (6 May 2026) and Erroneous claim for refund or credit (30 July 2026), 26 U.S.C. 6676.  Back
8. IRS, Tax preparer penalties (21 September 2026): 26 U.S.C. 6694 and 6701.  Back