What you chose, what you promised, and which drawing it was built to.
Between buying a plot and starting on site you appoint six or seven firms, make several hundred decisions about the house, accept a set of planning conditions you must discharge before anybody digs, and accumulate drawings that go through revisions nobody tracks. All four of those come back and ask you a question later. This is where each of them is kept.
Who you appointed, and who you have not
It opens as the roster of consultants a build may involve, not a blank list. Architect, architectural technologist, structural engineer, services engineer, civil engineer, ecologist, acoustic consultant, arboriculturalist, flood-risk consultant, and the statutory roles. You mark the ones you are actually engaging.

Five appointed, four not. The empty rows are the useful ones.
The roles you have left empty are the point. A stranger to construction does not know that an acoustic consultant might be a planning condition rather than a luxury, and a list that only shows who you have hired cannot tell you. Behind each appointment sit the terms you agreed, their contact details and what you have checked about them.
Every decision about the house, on one line each
One line per decision, in build order: what you chose, the product and the colour, who needs to know and when, and what you were told about the wait. It runs from the site compound and the temporary electricity supply to the ironmongery and the turf.

In build order, starting before there is a house.
The description is yours and in your words. Compound in the north-east corner, off the existing field gate, one container for tools and a separate one for materials, parking laid out so nothing reverses onto the road is a specification. A dropdown could not have held it, and the builder pricing the job needs exactly that sentence.

The same schedule filtered to one part of the build, with the reason behind each choice still attached.
Each line also carries why. Spend light, on purpose. Choose quiet. Eleven months later, when somebody asks why the landing insulation sits on legs over a boarded deck, the answer is on the line rather than in your memory. Lines you have not settled stay visibly unsettled — nothing is quietly filled in for you.
The conditions you have to discharge before you dig
A planning permission arrives with conditions attached, and some of them have to be discharged before you start — materials, drainage, the construction method statement, ecology mitigation. Others bite before you move in. Breaching one of the first kind can put the permission itself at risk, which is not something most people find out gently.

Every condition, in the order the decision notice prints them — or by the deadline you recorded, if that is the question you are asking.
The dates are the ones you entered off your own decision notice. We do not invent a deadline for you or work one out from an interval we made up: a rule is not a record. What we do is keep the dated events you recorded against each condition and the documents you attached as evidence, so a discharge is a thing you can produce rather than a thing you remember doing.
Which revision it was actually built to

Every drawing, every revision it has been through, and what went out to whom on what day.
A drawing that has been through P1, C and D is four drawings, and only one of them is the one the bricklayer had in his van. Keeping the revisions and the issue history is the whole of the answer when a wall is in the wrong place and everybody is holding a different sheet.
All four of these travel into the pack you leave with, filed under Design, The specification and Consents. More on the completion pack.