Glossary

United Kingdom. A form sent to HMRC before or with the Company Tax Return for every R&D claim. It asks for the contact details of every agent involved in the claim.1Source 1HMRC, Submit detailed information before you claim Research and Development (R&D) tax relief (26 September 2025). See United Kingdom.

A claim made by changing a return that has already been filed, usually for an earlier year. Each country sets its own time limits. See do you file amended or refund claims? and cold calls about unclaimed refunds.

A term that carries the engagement into the next year unless you give notice by a set date. See multi-year and renewal terms and automatic renewal clauses.

The amount a percentage fee is worked out on. An engagement letter may define it as the amount claimed, the amount received, or something wider, and the definition decides the fee. See what counts as the benefit.

The most a percentage fee can reach, stated as a figure. See capped fees and the script for asking for a fee cap.

On this site, the R&D tax credit, relief, offset or deduction a business asks for in its tax return, and the documents that support it. The business makes the claim in its own name, whoever prepares it. See who signs the claim.

A fee that is paid only if the claim succeeds, for example a percentage of the benefit. Also called a success fee. See contingent success fees.

The claim figure at which two fee models cost the same. Below it one model is cheaper, above it the other. See contingent versus fixed fees and the fee comparison calculator.

A fee that falls due later, for example when the credit is received, sometimes with an uplift for the wait. See deferred fees.

Australia. Registration of R&D activities with the Department of Industry, Science and Resources (DISR). A company applies within 10 months after the end of its income year.2Source 2Department of Industry, Science and Resources, Apply for the R&D Tax Incentive (business.gov.au). See Australia.

The contract between you and the adviser. It may refer to standard terms in a separate document, which are part of the contract too. See contracts and the engagement letter checklist.

A charge for ending the engagement, or for work or claims after it ends. See termination and exit fees and exit fees that lock you in.

What a percentage fee is a percentage of. See what exactly is the fee a percentage of? and unclear fee base.

The clause that sets the fee model and the rate. See fee basis.

An amount agreed in advance, whatever the size of the claim. See fixed fees.

Canada. The form on which a scientific research and experimental development (SR&ED) claim is made. Part 9 asks for claim preparer information, including the billing arrangement.3Source 3Canada Revenue Agency, T4088, Guide to Form T661, Part 9 (18 February 2026). See Canada.

New Zealand. Approval of a business's R&D activities by Inland Revenue, applied for before the R&D supplementary return is filed.4Source 4Inland Revenue, Research and development tax incentive due dates (1 April 2026). See New Zealand.

A fee for time spent, at a stated rate. An estimate and a ceiling make it comparable with other models. See hourly fees.

A fee with a fixed part and a percentage part. See hybrid fees.

A promise by one party to cover a loss of the other. In an engagement letter it can run either way. See liability and indemnity.

A limit on what the adviser pays if its work causes you a loss. See liability and indemnity.

The least the adviser charges, whatever the claim turns out to be. See are there minimum or exit fees?

How far ahead you must tell the adviser that you are ending the engagement. See termination and exit fees and the script for giving notice.

A percentage fee worked out on the amount you actually receive, not the amount claimed. See percentage of refund fees.

United States. The preparer tax identification number that anyone who prepares a federal tax return for pay must hold.5Source 5IRS, PTIN requirements for tax return preparers (16 October 2025). See United States.

A payment to someone for introducing a client to an adviser. See do you pay or receive referral fees? and the script for asking about referral fees.

A regular payment for the year's work, sometimes credited against a success fee. See retainer plus success fees.

A tax authority's check of a claim after it is filed. Countries use different names, such as examination, compliance check, enquiry, audit or intervention. See claim reduced on review and the "if your claim is reviewed" page for your country.

The adviser's help if the claim is reviewed: correspondence, meetings and revised calculations. Whether it is included in the fee is a term of the engagement letter. See review and audit support and is review support included?

Singapore. The Singapore Chartered Tax Professionals, described by IRAS as the accreditation body for tax professionals in Singapore.6Source 6IRAS, IRAS-Tax Agent relationship (28 January 2026). See Singapore.

A claim prepared largely through software, with or without an adviser's review. See software-assisted claims.

The adviser's general terms of business, referred to in the engagement letter. Renewal, notice and liability terms can sit there and not in the letter, so read them too. See multi-year and renewal terms.

Another name for a contingent fee. See contingent success fees and uncapped success fees.

Ireland. The tax advisor identification number an agent needs to act for a client with Revenue. Revenue says a TAIN is not an approval or endorsement of the agent.7Source 7Revenue, Tax and Duty Manual Part 37-00-04b, Guidelines for Agents or Advisors acting on behalf of taxpayers (September 2026). See Ireland.

The adviser's own calculation of its fee on a stated claim figure. Asking for one on your expected claim and on half of it puts proposals on the same basis. See how to compare proposals.

The calculations and notes behind a claim. Who owns them, and whether you get a copy, is a term of the engagement letter. See ownership of records and work and the script for requesting your records.