Decide what the index is for
An evidence index is not a document list. It is a map from a priced decision to the evidence that supports it. The decision might be a quantity, a unit rate, a productivity assumption, a subcontractor inclusion, or a risk allowance.
Start with the decisions that would change the bid if they were wrong, not with every file in the project. Write the purpose in one sentence and keep it visible. A useful purpose is: allow a reviewer who did not build the estimate to trace each major line to its source and approval in under ten minutes.
That standard shapes the index. It rules out a folder tree that only the original estimator can navigate.
Choose record keys that survive turnover
Use a key that does not depend on a person's name or a temporary file path. The cost code plus the estimate version is a good start. Add the source document identity, such as a drawing sheet and revision, a specification section, or a quote number with its date.
Keep one row per decision, not one row per file. A single decision may need a drawing, a quote, and a calculation.
The row points to all three, and the status shows whether the set is complete. This structure makes gaps visible without requiring the reviewer to open every attachment.
Link source, assumption, calculation, and approval
Each row should answer four questions. What source governs the value? What assumption did the estimator make?
Where is the calculation? Who approved the result? If any answer is missing, the row is incomplete and should be marked as such rather than filled with a generic note.
Use durable references. A shared drive path can change, and an email can be deleted, so store the evidence in the project record and link to that copy.
For external pricing, keep the dated quote or the index value that supports the rate. The material escalation clause review explains why the pricing date matters when the source is an index.
| Field | What to record | Review question |
|---|---|---|
| Decision key | Cost code and estimate version | Can the line be found without a person? |
| Source | Drawing, specification, or quote identity | Is the source current and governing? |
| Assumption | What the estimator had to assume | Is the assumption stated and bounded? |
| Calculation | Location of the quantity or rate math | Can a reviewer reproduce the result? |
| Approval | Owner, date, and condition | Who accepted the basis? |
| Status | Missing, stale, conflicting, or approved | What is the next action? |
Classify gaps instead of hiding them
Not every gap is equal. A missing source may be a documentation problem, while a conflicting source may be a design problem, and an expired quote may be a commercial problem. Use a small set of reason codes so the review can sort the work and assign the right owner.
A useful set is: missing, stale, conflicting, unverified, and approved with condition. The last code matters because some decisions are legitimately approved before every detail is known. The condition records what would reopen the decision, which is more honest than marking it complete.
Assign review ownership by decision type
The estimator owns quantity and pricing evidence. The chief estimator owns assumption and methodology. The commercial lead owns qualifications and risk treatment.
A project lead may own schedule evidence. Naming the owner by decision type prevents the index from becoming everyone's side task and no one's responsibility. Set a review cadence that matches the estimate stage.
At concept, the index may cover only the largest drivers. At bid, it should cover every line above a materiality threshold. The threshold itself should be written down so the team does not debate scope at the last minute.
Version the index with the estimate
An evidence index without a version can silently drift from the estimate it describes. Give the index the same version identifier as the estimate and record the date of the last change. When a revision or addendum changes a line, update the row and the version together.
Keep prior versions for the bid record. If a decision changes after review, the team should be able to see what was previously approved and why it moved. The drawing revision impact review is a natural trigger for an index update because it produces a defined delta.
Use the index at release and after award
At release, the reviewer samples rows against the actual evidence and records the result. The sample should include a high value line, a line with a recent change, and a line that was previously marked as a gap. If the sample fails, the index is not ready to support the release.
After award, the index becomes a handoff tool. The project team can see which assumptions were priced, which allowances remain open, and which sources were current at bid time. That context reduces the chance that a post-award change is priced twice or missed entirely.
A small index that is used beats a perfect index that is not
Start with ten to twenty decisions, not every line. Choose the largest values, the assumptions that would change the bid, and the items that changed late. Build the habit of updating the index when a revision or a quote arrives.
The index will grow naturally as the estimate matures. Review the index with the person who will use it after award. If the project team cannot follow it, simplify the fields rather than adding explanation.
The AACE recommended practices library is a useful reference for documenting an estimate basis without turning it into a second estimate. Assign one owner for the index and one reviewer for the sample. Without those two names the index becomes a shared document that no one maintains.
With them, it becomes a reliable map from a priced line to the evidence that supports it, which is the whole purpose of the exercise. Review the owner and reviewer names at each estimate version so the index does not outlive the assignment.
