An engagement letter is a formal written agreement between a professional services firm, such as an accountancy practice, and its client, setting out the scope of work, responsibilities, fees and terms governing the relationship. It is typically issued before work begins and reviewed or reissued periodically as the relationship continues.
How an engagement letter works
An engagement letter sets out exactly which services a firm will provide, such as annual accounts, tax returns or payroll, alongside the responsibilities of both firm and client, the fee basis, and terms covering data handling and limitation of liability. It is usually issued once client onboarding is complete, and firms following professional body guidance, such as that from ICAEW or ACCA, typically review and reissue letters annually or whenever the scope of work changes, so the terms in place always reflect what is actually being delivered.
How UK accountancy practices use engagement letters
- An accountancy practice issues a new engagement letter to a client whenever the scope of work changes, such as when adding payroll services to an existing annual accounts engagement.
- A firm reviews and reissues its engagement letters annually to ensure fee terms and responsibilities remain accurate and up to date.
- A practice uses standard engagement letter templates aligned to professional body guidance, such as ICAEW or ACCA, adapting them for the specific services each client receives.
- An advisory firm refers back to a signed engagement letter to clarify the agreed scope of work when a client disputes what was included in a fee.
How Advantage supports engagement letter management
Advantage's EdgeAdvisory accelerator helps accountancy and advisory firms track which engagement letters are current for each client, flagging renewals due and linking signed terms to the services being delivered within Dynamics 365.
Frequently Asked Questions
Is an engagement letter a legal requirement?
Not a general legal requirement, but professional bodies such as ICAEW and ACCA require members to have a letter of engagement in place with clients, and it is considered standard good practice across the accountancy profession.
What happens if the scope of work changes after an engagement letter is signed?
A firm typically issues an updated or supplementary engagement letter reflecting the change, so the agreed scope, responsibilities and fees stay current and clearly documented.
Why is an engagement letter important if a dispute arises?
It provides written evidence of what was agreed between the firm and client, helping resolve disagreements over scope, fees or responsibilities, and can be relevant to a professional indemnity claim if one arises.
