An engagement letter for bookkeeping exists to answer, in writing and before any work starts, the four questions that otherwise get answered in an argument nine months later: what is this practice actually doing, what is the client responsible for supplying, what does it cost and when is it billed, and how does either side end it. Most small practices know this and still send the first month's work off the back of a phone call, because the letter feels like a formality between people who already trust each other. It is not a formality. It is the only document that says what was agreed at the moment both sides still agreed, and the practices that never have a scope argument are the ones that write it down first and keep it where they can find it.
Scope, in the client's words and yours
The single most useful paragraph names the work by period and by task: monthly bank and credit card reconciliation for two accounts, coding to the client's chart of accounts, payroll journals entered from the payroll provider's reports, and a month-end pack delivered by a stated working day. Then it names what is NOT in the engagement, which matters more: tax return preparation, sales tax filing, payroll processing itself, an audit of any kind, and any judgement about whether a transaction was a good idea. A bookkeeping engagement that does not say what it excludes will be assumed to include whatever the client needed that month.
Client responsibilities, because the delay is usually upstream
Bookkeeping runs on records the client controls, so the letter has to put the obligation where the work actually stalls: bank statements and feeds kept connected, receipts and bills supplied by an agreed day, questions on the open items list answered within a stated number of business days, and management responsibility for the completeness and accuracy of what is provided. Two lines here save an entire category of dispute, because the client who is two weeks late with statements and then asks why the accounts are late has already read the answer and signed it.
Fees, billing and what happens when the work grows
Fixed monthly fees are the norm for bookkeeping and they are only safe when the letter says what happens outside the fixed scope. Name the fee, the billing date and the payment terms; then name the trigger for a change, which is usually a transaction volume band, an extra bank account, a catch-up period, or a request for work the exclusions list already ruled out. A letter that says out-of-scope work is quoted separately and agreed in writing before it starts turns an awkward conversation into a clause that was already read.
Termination, records and where everything lives
Say how either side gives notice, what is delivered on the way out, and what the practice keeps. Working papers belong to the practice, the client's own books and source documents belong to the client, and the letter should not leave that to be worked out under pressure. Retention is a real obligation rather than a housekeeping preference: the IRS sets record retention periods for the underlying business records, and a practice that keeps client documents in a portal with a dated history can answer a request years later without a search through email. That is the point at which the engagement letter stops being paperwork and becomes the first entry in a client's file.
Questions people ask about engagement letter for bookkeeping
Does a bookkeeping engagement need a letter if I am not doing tax work?
Yes, and arguably more so. Tax work has a filing deadline that forces scope to the surface; bookkeeping drifts, one small favor at a time, until the fixed monthly fee covers three things nobody agreed to. The letter is what makes the drift visible.
What is the difference between an engagement letter and a contract?
In practice, none that matters: a signed engagement letter is a contract. The name is a professional convention, and the reason it reads as a letter rather than a deed is that it is written to be understood by the client who signs it.
Do I need a new letter every year?
Reissue it when the scope, the fee or the responsible people change, and at least annually for a recurring engagement. A three-year-old letter describing work you no longer do is worse than no letter, because it is evidence of a different agreement.
Where should the signed letter be kept?
Against the client record, with the date it was signed and the version that was signed, not in an email thread. Tickmarko keeps the engagement with the client's documents and requests so the version in force is the one anyone in the practice can find.