Key takeaways
- An engagement letter defines one engagement, while a master services agreement holds terms that repeat across engagements.
- Name the tax years and return types in the letter, and state that later years are not covered.
- Audits, reviews and compilations require a written letter under the standards, and NASBA calls one best practice for tax work.
- A Section 7216 consent needs its own signed and dated form, and the engagement letter cannot replace it.
What each document does
An engagement letter is the firm’s agreement for one defined piece of work: a 2026 Form 1040 for a sole proprietor, a twelve-month bookkeeping close, or a one-time cleanup of 2025 books. It sets the scope, exclusions, fee, client duties, timing and the signatures that bind both parties.
A master services agreement (MSA) holds the terms that repeat across engagements with one client: liability, confidentiality, data handling, payment terms, dispute resolution and governing law. It does not describe the work.
A statement of work (SOW) describes one project, its deliverables, dates and fee, and refers back to the MSA. The NJCPA’s 2026 summary says each new service under an MSA gets its own SOW, which incorporates the MSA by reference.
Scope: the sentence that prevents the next dispute
NASBA’s guidance on tax engagements says to identify the periods, state that the engagement pertains only to the specific tax year or years, and identify the type of return being prepared. Those items answer the question a client asks when the next return arrives: was it included?
For a single-year return, the scope clause can read: “Scope. We will prepare the 2026 federal Form 1040, including its business income section, for the taxpayer named above. We will not prepare any other federal or state return, any amended return or any notice response unless it is listed in Exhibit A and signed by both parties. Each later tax year requires a new engagement letter or a signed renewal.” That closes the question before the next return arrives.
Recurring bookkeeping needs a different scope clause. Name the entities, the accounts, the months covered and the deliverables, then list the exclusions. If the letter says nothing about vendor information returns, a client who expects the firm to prepare them in January will read the silence as included.
Liability and dispute terms: what goes in the letter
The NJCPA article lists the provisions firms use to limit exposure: arbitration or mediation language, a limitation of liability, a venue and governing-law clause, a stop-work clause and a fraud-detection statement. It recommends placing provisions that restrict a client’s legal rights in the engagement letter rather than a separate terms-and-conditions document. Have counsel check that against your state’s law.
The statute of limitations is the hard problem with an MSA, because an MSA can run for years and the date a claim starts running is hard to pin down. Restate the key dates and terms in each SOW or letter so each engagement carries its own record.
Decision rule: if the client has multistate payroll, sales tax registrations in more than one state or an open IRS notice, put the dispute and limitation terms in the letter itself and have counsel review the wording. A single-owner client with one bank account needs a short letter with a termination clause.
What the professional standards and state boards expect
For audits, AU-C 210 requires a written agreement on engagement terms, according to the NJCPA’s summary. For compilations, reviews and preparation engagements under the SSARS standards, AR-C 60 and the related sections call for a signed engagement letter.
For tax and bookkeeping work the picture is looser. NASBA says engagement letters are required for attest services but not for certain other accounting services, and that best practice still favors using them, especially for tax services.
State boards decide the discipline question. NASBA reports that the first question most Board of Accountancy investigators ask a respondent is, “What does your engagement letter say?” The answer is whatever the firm wrote, so the letter has to match what staff actually do.
Section 7216 consent is a separate signed document
A paid tax return preparer generally cannot use or disclose a client’s return information for another purpose without the taxpayer’s written consent. Under Section 7216, a violation is a misdemeanor with a fine of not more than $1,000 and up to one year in prison. The civil penalty under Section 6713 is $250 for each disclosure or use, with a calendar-year maximum of $10,000.
Under Section 301.7216-3, the taxpayer must sign and date the consent. If the consent does not state how long it lasts, it is effective for one year from the date the taxpayer signed it. Several common disclosures need no consent under Section 301.7216-2. A preparer may share return information with another U.S. preparer who helps prepare the return, as long as that preparer makes no substantive determinations. A preparer may also send it to an Authorized IRS e-file Provider for electronically filing the return, or to a tax return processing service. A contractor doing programming, maintenance, repair or testing of tax preparation software may receive it too, but only after the preparer has given that contractor written notice of Sections 6713 and 7216.
Sharing return data for any other purpose needs a consent that covers that use, and the engagement letter cannot stand in for it. A bookkeeping partner that receives return data for work that does not feed the return is one example, and a referral or marketing use is another. A disclosure to a recipient outside the United States needs the taxpayer’s consent before it happens, under Section 301.7216-2(c)(2).
Keep the documents separate. Form 8879 is the declaration document and signature authorization for an e-filed return, so it belongs with the return. Form 2848 authorizes an individual to represent the taxpayer before the IRS.
Decision rules by engagement type
Recurring bookkeeping or a monthly close: use an engagement letter with a renewal clause. Set the fee, the account list and the deliverables, and state that the agreement renews each January unless either party gives written notice by a fixed date, for example 30 days before renewal.
One annual return: use a letter that names the tax year and return types. Ask for a new letter every year, because the tax year changes the facts, the fee and the forms.
One-time project, such as a 2025 books cleanup, a sales tax lookback or a back-year catch-up: use an SOW or project letter with dates, deliverables, a fixed or capped fee and a stop-work clause. State what the firm will not do, such as filing the 2025 return or answering a state notice, and say those items need their own letter.
When a firm needs both an MSA and letters
Most firms of 2 to 15 people do not need a master agreement on day one. An MSA starts to pay off when the same client buys several services over several years and the firm wants one set of data, confidentiality and payment terms across all of them.
A workable setup for a client buying bookkeeping, payroll and an annual return: one MSA for the relationship, one renewable letter for the bookkeeping, one letter for each annual return and one SOW for each cleanup project. Each document names the MSA by title and effective date. Counsel should review the MSA every one to two years.
Failure modes and fixes
Failure: the letter names the 2025 return and no later year, but staff keep working on the 2026 return from the same file. Fix: calendar a renewal review each November.
Failure: the client signs a letter that refers to an MSA the client never received. Fix: attach the MSA as an exhibit, or send a link the client can open before signing, and record the date it was sent.
Failure: a fee change goes out by email while the signed letter still shows the old fee. Fix: write the notice rule into the letter itself.
Clauses to copy
Term. This engagement covers calendar year 2027 only. It ends at the close of calendar year 2027 unless a new letter is signed by both parties.
Client duties. The client will provide the documents listed in Exhibit A by the dates shown. If documents are not received by those dates, the firm may pause work and will tell the client in writing before it does.
Fees. The monthly fee is [monthly fee], billed on the first day of each month. A change in the fee takes effect after 30 days’ written notice to the client.
Acceptance. Please sign, date and return this letter by [date].
Timing for 2026 tax year work
Send letters for 2026 work in November and December 2026, before year-end bookkeeping starts. A letter sent in March leaves a return in progress with no agreement covering it.
If a client signs after work has started, record both the signature date and the date of first work. Those two dates show any gap in written scope.