The expert report total differs from its cost model: trace the calculation
A report and its attachment show different totals
The expert report puts one figure on rectification, while the attached cost model appears to produce another. Avoid picking whichever figure favours your business. Establish what each total represents and whether both belong to the same version. The immediate task is a traceable question about the calculation, not a declaration that the report or the underlying technical assessment is worthless.
Preserve the supplied model
Keep the original report, attachment and covering correspondence unchanged. If you are permitted to inspect a spreadsheet, work on a copy and record its filename and date. Do not overwrite formulas, remove hidden rows or refresh external links in the original. Ask your lawyer about obtaining a readable calculation where the document supplied does not show how the total was built.
Follow the bridge to the narrative
Record the model output, the report figure and any explained adjustments between them. The Judicial Commission of NSW's discussion of opinion evidence emphasises identifying the facts and reasoning supporting an opinion. That does not entitle you to demand any particular file. It supports asking your adviser a precise question about an unexplained calculation rather than making a broad accusation about the expert.
Consider a hypothetical mismatch
Imagine a model subtotal of $82,000 and a report total of $90,200. The difference might reflect an explained tax adjustment, an additional cost or an earlier spreadsheet version. Write down those possibilities as questions. Until the basis is checked, neither the difference nor an apparently convenient percentage proves a mistake, an inflated claim or the amount your business must pay.
Separate arithmetic from professional choices
An apparent duplicated row or broken formula needs a different question from a disputed repair method or contingency allowance. Flag the exact cell, page and calculation without substituting your own technical judgment. Let the lawyer and appropriately qualified expert decide how to seek clarification and evaluate the assumptions. Keep any responses with the version they explain so later corrections remain understandable.
Use a small reconciliation note
Provide your adviser with the two totals, the calculation path you can follow and the point where it stops. Ask whether clarification changes the amount under discussion, the technical evidence or neither. Continue meeting the actual proceeding's requirements while that question is resolved. A calculation review is useful when it makes the uncertainty specific; it does not itself determine admissibility, liability or the appropriate remedy.