To update your MTD engagement letter, six clauses in your existing Self Assessment letter must change: scope of services, agent role, client responsibilities, fee arrangement, data and software, and penalty exposure.
Easier said than done, though.
An engagement letter has to protect the firm, set out the client’s obligations precisely, declare the agent role, and cover what happens when someone leaves mid-year. One ambiguous clause and the whole thing unravels, whether in a client dispute, a professional indemnity claim, or a regulatory review. That is a lot of ifs, what-ifs, and risk for the firm.
That is what this post covers: a practical, clause-by-clause guide to updating your existing engagement letter for MTD clients, or if you are starting fresh, writing a new one. Plus a free sample MTD engagement letter template, and a tool that produces a fully compliant one in seconds. Thirty, to be fair.
This guide assumes familiarity with MTD for Income Tax scope and thresholds. If you are starting from scratch, read this first: MTD for Income Tax: A Complete Guide for Accountants and Agents
Does My Existing Engagement Letter Work for MTD?
No. Your existing Self Assessment engagement letter will not cover MTD. It describes one deliverable: preparation and submission of the annual return. An MTD engagement letter must cover at least five filings per qualifying business, ongoing digital record management, quarterly client data collection, and a Final Declaration.
The structural differences go further than the filing count:
- Under Self Assessment, the client provides information once a year. Under MTD, they provide it four times, to a firm deadline each quarter. That obligation must be written into the engagement
- Under Self Assessment, there is no question of data ownership. Under MTD, the digital records in the software are the bookkeeping record of record, not a working paper. Who owns that data, who can access it, and what happens to it on termination are live contractual questions
- Under Self Assessment, agent roles do not need to be distinguished. Under MTD, Main agent and Supporting agent are separate HMRC designations with different scopes of authority. A letter that does not specify which role the firm holds leaves the practice exposed to claims beyond its contracted scope
The Six Clauses That Must Change in Your MTD Engagement Letter
Six clauses. That is all that stands between your existing Self Assessment engagement letter and a fully compliant MTD one. Each reflects a structural change in how the service is delivered, not just a change in the number of filings.
The clauses are: scope of services, agent role, client responsibilities, fee arrangement, data and software, and penalty exposure.
1. Scope of Services
The old wording: “preparation and submission of your Self Assessment return.”
That single line does not describe MTD. The scope clause must be replaced with an itemised list of MTD deliverables. At minimum, the letter should specify:
- Maintenance of digital records in MTD-recognised software
- Review of client-submitted transactions, or data capture by the firm where the firm manages the bookkeeping
- Preparation and submission of four quarterly updates per qualifying business
- Preparation and submission of the Final Declaration
- Handling HMRC correspondence related to MTD obligations
- Any advisory services that are explicitly included or explicitly excluded
Each qualifying business must be listed separately. A client with a sole trader business and two buy-to-let properties has three sets of MTD obligations. The MTD engagement letter must name each one and specify the scope for each.
2. Main Agent or Supporting Agent
Under MTD, HMRC distinguishes between two agent types. Which one your firm holds determines what you are authorised to do and what you can be held responsible for.
If the firm is acting as Supporting agent, the MTD engagement letter must say so explicitly, and must state what is excluded:
- We will file quarterly updates only.
- We will not file the Final Declaration.
- We will not handle HMRC correspondence related to MTD obligations.
- We will not manage the client’s MTD authorisations.
- The client must arrange the Final Declaration separately, either with their Main agent or personally.
The agent role is not implied by the work the firm does. An MTD engagement letter that leaves this ambiguous exposes the firm to claims beyond its contracted scope.
3. Client Responsibilities
Clients have significantly more to do under MTD than under Self Assessment. The engagement letter must say so clearly, and must specify what the client is expected to provide, in what format, and by when.
At minimum, the client responsibilities clause should cover:
- Provide complete and accurate data by the agreed quarterly cut-off date
- Use the nominated software, or an agreed alternative, to capture transactions as they occur
- Promptly forward letting agent statements, HMRC correspondence, and any documents received
- Notify the firm of changes to properties, tenancies, or business operations that affect qualifying income
- Review and approve quarterly submissions before filing, or provide standing authority to file without per-quarter approval
That last point requires a specific decision, documented in the letter.
WARNING: The Standing Authority Decision
Some clients will want to approve every quarterly submission before it is filed. Others will grant standing authority, allowing the firm to file without waiting for confirmation each quarter. Both are acceptable. The choice must be recorded in the MTD engagement letter. A client who later disputes a filing cannot credibly claim the firm acted without authority if standing authority is documented. A firm that filed without authority because the letter did not address it has no defense.
4. Fee Arrangement
Annual fixed fees do not work well for a quarterly service. A client can leave mid-year. Scope can change mid-year. A fee that looked right in April may not reflect the actual work by October.
The fee clause must specify:
- The total annual fee and the billing frequency: monthly, quarterly, or annually
- What is included in the fee: number of properties, number of quarterly updates, advisory calls, HMRC correspondence handling
- What triggers a re-quote: additional property, change of ownership structure, new qualifying business, switch from self-entry to firm-managed bookkeeping
- How out-of-scope work is priced and billed
- The payment method
Chasing invoices every quarter, on top of chasing data, is an avoidable problem. Automated payment via direct debit or card subscription removes it entirely.
The fee clause is only as good as the fee behind it. Read: How to Price MTD ITSA Services: A Comprehensive Guide for Accountants and Tax Advisers
5. Data & Software
This clause does not exist in a standard Self Assessment engagement letter. MTD changes that.
The digital records maintained in MTD software are the bookkeeping record of record. They belong to the client. The MTD engagement letter must address five questions:
- Who owns the data in the software during the engagement?
- Who has access to the data during the engagement?
- What happens to the data if the engagement ends? Can the client export it in a usable format?
- What happens to the software subscription if the client leaves? Does the firm cancel it, or does the client take over?
- Will the firm retain copies of the data for its own records after termination?
These are not theoretical. A client who leaves mid-year needs access to their digital records to continue filing with a new accountant. If the records are locked in the firm’s software subscription, the transition becomes adversarial. The exit path should be clear before the engagement starts, not when a client is already leaving.
6. Penalty Exposure
Who bears the penalty if a quarterly update is filed late?
The answer depends on why it was late. The MTD engagement letter must make the distinction explicit:
- If the firm files late because the client did not provide data by the agreed cut-off date, the client bears the penalty consequence
- If the firm files late despite having the data on time, the firm bears the professional responsibility
- The letter should specify the quarterly cut-off date for each business, and state what the firm will do if data is not received: file based on available information, or not file and notify the client of their penalty exposure
WARNING: Build the Penalty Framework Into the Letter
Every practice will eventually have a client who provides data late and receives a penalty point. With a clear engagement letter, it is a professional conversation about deadlines. Without one, it becomes a complaint. The penalty point system under MTD is cumulative: two points triggers a £200 fine, four points triggers a £200 fine per subsequent failure.
Special Cases: MTD Engagement Letters That Need More
For most MTD clients, the six clauses above are sufficient. Two client types need additional provisions on top.
Joint Ownership: Two Clients, Two Engagement Letters
Each co-owner of a jointly held property is a separate MTD client with separate quarterly obligations, separate deadlines, and separate penalty exposure. One MTD engagement letter covering a household is not defensible.
Each letter must specify the properties covered and the ownership percentage for each, the co-owner’s individual mandation date, and the fee for that person’s MTD obligations specifically.
It is tempting to treat a married couple as one commercial relationship. The regulatory obligations are individual. Two letters is the correct approach.
Non-Resident Landlords
Non-resident landlords are exempt from MTD for 2026/27. Most will be mandated from April 2027, when the threshold drops to £30,000 qualifying income. Clients without a UK National Insurance number may be permanently exempt under the no-NINO provision. Check each client’s position individually.
The standard six clauses apply. The MTD engagement letter for a non-resident client must also cover:
- The MTD start date: April 2027 for most, but potentially later for clients below the threshold or permanently exempt via the no-NINO route
- Whether the firm manages the Non-Resident Landlord Scheme position alongside MTD, or handles MTD filing only
- How letting agent statements will be obtained: directly from the agent, or via the client
- The client’s responsibility to provide data within a set number of days after each quarter-end, adjusted for time zone differences
- How Final Declaration approval works for a client outside the UK, including the method and the response deadline
- Whether the firm advises on the interaction between UK tax and the client’s local tax position, or whether the client must instruct a separate adviser
- The fee basis, noting explicitly that quarterly filing for non-resident clients involves additional work compared to UK-resident clients
Re-Papering Existing Clients
Every existing Self Assessment client who moves into MTD needs a new MTD engagement letter. Clients mandated from April 2026 should be re-papered before the first quarterly deadline: 7 August 2026.
That window is tighter than it looks. Re-papering must happen before sign-up, authorisation, software setup, and first-quarter data capture. It is not the last step. It is the first.
The process for a client base of any size:
- Identify in-scope clients. Use the 2024/25 Self Assessment data. Gross qualifying income above £50,000. It is gross rents and gross turnover before expenses, not net profit
- Draft the MTD engagement letter template. One master template covering all six clauses, with variables for the client’s specific properties, businesses, ownership splits, and fee tier
- Issue in batches. Send in cohorts of 20 to 30 clients to allow time for queries, re-quotes, and pushback
- Track responses. Monitor who has signed, who has opened but not responded, and who has not opened at all. Chase non-responders before the deadline, not after
- Handle pushback. Some clients will resist the new fee. A client who cannot accept the MTD price is a client the practice cannot afford to keep at the old price
WARNING: Re-Papering Takes Longer Than Practices Expect
Allow two to three months for a client base of any size, not two to three weeks. Each letter needs to be tailored. Clients take days or weeks to read, query, and sign. Fee conversations slow everything further. The practices that are ready started early. The ones that are not, did not.
Sample MTD Engagement Letter
Here is what a fully drafted MTD engagement letter looks like in practice.
This is a sample MTD engagement letter for illustration purposes only. All names, addresses, and client details are fictitious.
The sample covers all six clauses: scope of services, agent designation, client responsibilities, fee arrangement, data and software provisions, and penalty exposure.
You can also get a fully customisable version here: MTD ITSA Engagement Letter Templates
We Said MTD Engagement Letter in Seconds. We Meant It.
Remember that promise from the intro? Here it is.
Drafting from scratch, tailoring per client, chasing signatures, tracking who has opened and who has not. That is the manual way. It works, but it takes time most practices do not have, especially when re-papering 50, 100, or 200 clients before the first quarterly deadline.
FigsFlow generates a fully compliant MTD engagement letter directly from the proposal scope. Change the client type, services, or fee and the letter updates automatically. Every clause covered. E-signature and response tracking built in.
Thirty seconds. That is all.
Book a demo, start the timer, and see it for yourself. Sometimes it takes a minute though. Server side issue.
Conclusion
An MTD engagement letter is not a patched version of a Self Assessment letter. It is a different document, covering a different service, with six clauses that must change: scope of services, agent role, client responsibilities, fee arrangement, data and software, and penalty exposure.
Get those right and the letter holds up. Leave any one ambiguous and it will not.
Further reading: Once your MTD engagement letters are in order, the next step is building an efficient onboarding process for MTD clients. Read this next: How to Onboard MTD Clients Efficiently in 2026 | FigsFlow
