Scope of work
Which returns, filings or services the firm will handle, and for which tax years or periods. The narrower the wording, the clearer it is later.
Tax & CPA workflow
What is an engagement letter?
An engagement letter is a written agreement between a client and an accounting firm that sets out what work the firm will do, what it will cost, and what falls outside the arrangement. It is signed before the work begins, and it is what both sides point to if a question comes up later about what was agreed.
What an engagement letter covers
Letters vary by firm and by the kind of work, but most cover the same six things.
Fees and billing
What the work costs, whether it is a fixed fee or hourly, when invoices arrive, and what happens if the work turns out larger than expected.
What is excluded
Everything the firm is not doing. Audit representation, prior-year amendments, and state filings beyond the ones listed are common exclusions.
Client responsibilities
What you have to provide and by when. Firms usually state that they rely on the information given without independently verifying it.
Timelines and deadlines
When documents are due to the firm, and what happens to your filing if they arrive late.
Term and termination
How long the arrangement runs, how either side ends it, and what happens to your records afterwards.
Why firms send one before starting work
An engagement letter exists to make the boundary of the work explicit before anyone relies on it.
Most disagreements between a firm and a client are not about the quality of the work. They are about whether something was inside the job. A client assumes the firm is watching for a state filing requirement. The firm assumed the client would mention the second state. Nobody was careless, and both remember the conversation differently.
Professional bodies recommend engagement letters for exactly this reason, and most professional liability insurers ask whether a firm uses them. A signed letter that names the scope is the difference between a conversation and a claim.
The other reason is less defensive. Writing the scope down forces both sides to notice what has not been discussed. Clients read the exclusions and realize they need something that is not on the list, which is a much better time to find out than March.
What to read twice before you sign
The scope section
Check the years, the entities and the filings named. If you own a business, a letter covering only your personal return does not cover the business one.
The exclusions
Read the list of what is not included. This is where you find out that state filings, amended returns or responding to an IRS notice are billed separately.
How fees change
Look for the wording that covers work turning out larger than expected. Most letters allow the firm to bill more; the question is whether they have to tell you first.
Your own obligations
Firms usually state that they rely on the information you provide. That places the accuracy of what you hand over squarely on you.
What happens if you leave
Check how the arrangement ends and what happens to your documents. Firms are generally required to return your original records, though their own working papers stay with them.
Engagement letters for bookkeeping services
Bookkeeping engagements work differently from tax engagements, and the letter reflects that.
A tax engagement letter covers a defined piece of work with an end point. A bookkeeping engagement letter covers ongoing work with no natural end, so it has to be specific about frequency and volume rather than deliverables. Monthly reconciliation of three accounts is a different arrangement from monthly reconciliation of eleven, and the letter needs to say which.
Most bookkeeping engagement letters cover the same six areas listed above, plus a few that only apply to continuing work:
The cycle. Whether the books close monthly, quarterly or annually, and when each period is finalized.
Volume assumptions. Transactions per month, number of accounts, number of employees on payroll. Fees usually assume a range, and the letter says what happens outside it.
Access to systems. Which accounting software is used, who owns the subscription, and what access the firm holds.
Where bookkeeping stops. This is the important one. A bookkeeping engagement letter should say clearly whether the firm is preparing financial statements, and whether anyone is reviewing or auditing them. Bookkeeping, compilation, review and audit are four different services with four different levels of assurance, and a client who assumes they are getting one while paying for another is the most common misunderstanding in the field.
Rolling term. Bookkeeping letters usually renew automatically rather than running to a fixed date, with a notice period for either side to end them.
Tax preparation engagement letters
A tax preparation engagement letter is the most common kind, and the most specific.
It names the tax year, the returns being prepared, and the jurisdictions. "Federal Form 1040 and California Form 540 for tax year 2026" is the level of detail to expect. Anything not named is not included.
Three things appear in most tax engagement letters and surprise people who have not read one before.
The firm relies on what you tell it. Preparers are not auditing your figures. If you say charitable giving was four thousand dollars, that number goes on the return, and the responsibility for it stays with you.
Extensions are usually separate. Filing an extension is often listed as its own service rather than as part of the return, and it may be billed separately.
Representation is almost always excluded. If the IRS asks a question about the return afterwards, dealing with it is generally a new engagement with its own letter and its own fee.
What is a disengagement letter?
A disengagement letter is the letter that ends the relationship. It is sent by the firm when it stops acting for a client, and it does the opposite job of an engagement letter: it establishes clearly when the firm's responsibility stopped.
Firms send them when a client leaves, when the firm resigns from an arrangement, or when work concludes and nothing further is planned. A good one states the date the relationship ended, what work was completed, what was not completed, and any deadline the client now needs to handle themselves.
That last part matters. A client who leaves a firm in February may not realize that nobody is now watching their filing deadline. A disengagement letter that names the date and the outstanding obligation removes any argument about who was responsible.
If you receive one, read the section on outstanding items and record retention. It tells you what you need to pick up and how long the firm will hold your documents before disposing of them.
Engagement letter software
Engagement letter software handles the writing, sending, signing and renewing of these letters at volume.
The problem it solves is a firm-side one. A practice with four hundred clients sends four hundred letters, each slightly different in scope, and needs every one signed before work starts. Done manually that is a template, a mail merge, a chased signature and a spreadsheet tracking who has returned what.
Software in this category generally offers a template library with clause options for different services, per-client customization, electronic signature, tracking of who has signed and who has not, automatic renewal for continuing engagements, and a searchable archive of past letters.
Firms usually adopt it for a specific reason rather than a general one. Either the season started and thirty percent of letters were still unsigned in February, or an insurer asked to see the letters for a particular year and producing them took a week.
The category overlaps with practice management software, and many firms get engagement letters as one module of a larger system rather than as a standalone tool.
Engagement letter vs tax organizer
Both arrive early in the relationship and both come from the firm, which is why they get confused.
An engagement letter is a contract. It defines the work, the fee, and the boundary. You sign it, and it is binding on both sides.
A tax organizer is a questionnaire. It collects the information the firm needs to do the work. You fill it in, and nothing about it is binding.
The order is fixed. The letter comes first, because a firm should not start collecting a client's financial information before the terms of the work are agreed. The organizer follows once the letter is signed.
The document request list follows that same sequence by naming the files needed to complete the work.
One way to remember it: the engagement letter is about the relationship, and the organizer is about the return.
When an engagement letter gets updated
A letter covers what it names, so anything it does not name usually needs a new one.
Most firms issue a fresh letter each year, even for clients whose arrangement has not changed. Sending an annual letter is simpler than arguing later about whether a three-year-old letter still applies.
Beyond the annual refresh, a new or amended letter is normal when the scope changes mid-year, when a client adds an entity, when the fee arrangement changes, or when the client's circumstances change enough that the original scope no longer describes the work.
If your situation changed and you have not received a new letter, it is worth asking. The gap between what a letter covers and what a firm is actually doing is where problems start.
For firms: what makes an engagement letter hold up
Firms that avoid scope disputes tend to write letters the same way.
They name the exclusions explicitly rather than relying on what the scope implies. A letter that lists what is covered leaves everything else ambiguous. A letter that also lists what is not covered does not.
They send the letter before any work starts, including before collecting documents. A letter signed in March covering work that began in January is worth much less than one signed in January.
They reissue annually rather than relying on a rolling letter from three years ago, because the client's circumstances moved even if the arrangement did not.
They track signatures as a gate rather than as a task. The firms with a problem in February are usually the ones where signing was a reminder rather than a precondition for starting.
They keep the letters findable. When an insurer or a regulator asks for the engagement letter covering a particular client and year, it should take minutes.
Answers at a glance
Common questions
Yes. An engagement letter is a contract between the client and the firm, and both sides are bound by what it says. That is the reason it exists: it records what was agreed in a form neither party can later remember differently.
An engagement letter is the contract defining what the firm will do and what it charges, and you sign it. A tax organizer is a questionnaire collecting the information needed to do that work, and it is not binding. The letter comes first.
Most firms will not begin work without one, so in practice yes. If something in the letter does not match what you discussed, raise it before signing rather than afterwards. Firms amend letters routinely.
A bookkeeping engagement letter covers ongoing bookkeeping work rather than a one-time filing. It sets out the cycle, the assumed volume of transactions and accounts, which systems the firm has access to, and whether the work includes preparing financial statements.
A disengagement letter ends the relationship between a firm and a client. It records the date the firm stopped acting, what work was completed, what was not, and any deadline the client is now responsible for. It protects both sides by fixing when responsibility ended.
Most firms issue a new letter every year, even when nothing has changed. A new letter is also needed when the scope changes, when a client adds an entity, or when the fee arrangement changes during the year.
Engagement letter software creates, sends, tracks and renews engagement letters at volume. It typically includes a clause library, per-client customization, electronic signature, tracking of unsigned letters, automatic renewal, and a searchable archive.
Check the scope names the right years and entities, read the exclusions to see what is billed separately, look at how fees change if the work grows, and check what happens to your documents if you leave the firm.
Usually not. Representation before the IRS is almost always excluded from a preparation engagement and handled as separate work with its own letter and fee. Check the exclusions section of your letter to confirm.
The firm will normally raise it and either amend the letter or issue a new one for the additional work. Work done outside the agreed scope without a written change is where fee disputes usually start.
Related terms
What happens after the letter is signed
An engagement letter defines the work. The next step is collecting everything needed to do it, which is where most of the season goes. TaxFlo, one of the AmitaSoft platforms, runs that part: it asks each client only the questions their situation calls for and starts from what the firm already holds from last year.
Read about TaxFlo →