Essay
Drawn from current pipeline sizing, not a delivered case.
The example is drawn from current pipeline sizing, not a delivered case. It describes the shape of an HMRC investigation document pack Build at a mid-market tax advisory firm, and it is how we size the work at the end of Discovery. When the first Build ships and the firm signs off on a public case study, this essay gets a companion with measured numbers.
The people
On a Build of this size, two engineers, one senior and one mid-level, both named in the engagement letter, with part-time design help for the internal screens. From the firm: one business sponsor, usually the managing director of the relevant business; one subject-matter lead, a senior paralegal or a partner; and one IT contact who can grant access to the document store. Nobody else needs to be in the room.
The weeks
Weeks 1 and 2: Discovery, already done
The Build only starts once Discovery has produced a workflow map, a plan and the arithmetic. By the time a Build is scheduled, the firm knows what it is getting, and so do we. The numbers that anchor the refund clause are in the engagement letter.
Weeks 3 and 4: scaffolding
Sign-in through the firm's identity provider. Read-only access to the document store. The ingestion pipeline that will read the client history. A small internal web app behind single sign-on, with its first two pages. At the end of week 4 the sponsor can log in and see something skeletal but real.
Weeks 5 and 6: the actual work
The reasoning core: document extraction, timeline construction, citation handling, privilege flagging. The first five real client cases run through in parallel with the existing paralegal process, and the senior paralegal compares both outputs. We tune against the disagreements.
Weeks 7 and 8: hardening and handover
Error handling, permissions, audit logging. The tuning playbook gets written. The Managed retainer takes over. The Build has shipped.
The artefacts
- Engagement letter
- Scope, fixed price, the six-month payback clause keyed to the Discovery targets, named engineers, IP assignment and the data processing agreement.
- Architecture note
- One document, about twelve pages, in plain English. The thing the firm's next engineer reads in one sitting.
- DPIA
- Drafted inside Discovery and signed at the start of the Build. A live document for the Managed retainer.
- Source code
- In a Git repository the firm owns. Not a black box.
- Tuning playbook
- The operating manual for the firm's Managed contact: what to monitor, what to change, when to call us.
- Case study draft
- Numbers, method and the firm's name, only if the firm is willing to go on record. No surprise press.
How we size the fee
The Build fee is anchored in the Discovery arithmetic, not in a price list. For the HMRC investigation document pack, the sizing reads like this: thirty paralegal hours and three partner hours per complex enquiry today, a target of eight and one after the Build, and around a hundred enquiries a year. At mid-market tax-advisory loaded rates, that supports a Build in the forty-five to sixty-five thousand pound range, paid back inside six months. Those are sizing numbers set at the end of Discovery, not delivered results; the engagement letter binds us to whatever numbers we agree with the firm.
If the numbers do not land against the targets in the letter inside the refund window, the Build fee is refundable. We write that into the letter because the question of whether the Build was worth doing should be the firm's to answer, not ours, and the way of answering it should be signed by both sides, not asserted by one.
Eight weeks. Two engineers named in the letter. A codebase small enough to read in a sitting. A case study only if you want one.
The working, line by line, is on How we work; Fig. 1 runs it with your numbers. More on the writing page.