Start by comparing the same estimate
Before correcting prices, confirm that source and destination represent the same revision, currency and scope. One total may include costs that the other program shows separately. Ask the sender for the original file and a chapter summary generated at the same time. Keep an untouched copy and record the application, version and import options. A filename and download date are not sufficient to identify a revision.
Separate format validation from value reconciliation
FIEBDC publishes the format and a BC3 checker. Use these as references when checking the exchange structure, then reconcile values inside the applications involved. An import without errors does not establish that the receiving application retained every field your workflow needs. A matching total does not prove that every quantity and rate is correct either: two errors can cancel each other out.
Work down from total to chapter and item
Prepare a comparison table containing code, unit, quantity, rate and amount in each system. Compare chapters to locate the difference, then inspect their items. Prioritise large variances without dismissing repeated small discrepancies. If codes are missing, investigate chapter selection and import rules before changing calculations. Check whether the receiving program groups concepts that were previously separate.
Worked example: rounding can change the answer
Illustrative calculation: 12.345 units at €7.891 produce €97.414395, displayed as €97.41 when the result is rounded to two decimal places. If quantity and rate are first rounded to 12.35 and 7.89, the product is €97.4415, displayed as €97.44. The difference is €0.03. This does not itself establish a BC3 defect; it points to calculation precision and the stage at which rounding occurs.
Check measurement lines and resource coefficients separately
When quantity differs, compare measurement lines and subtotals: dimensions, signs, formulas and omitted lines. When the rate differs, review the resource breakdown and its coefficients. Avoid changing quantity, resource coefficients and prices simultaneously merely to make the total agree. Change one condition at a time in a test copy and record which discrepancy it explains.
Progress valuations: check current and cumulative values
In a valuation workflow, establish whether you are comparing current-period work or cumulative work. Retain the link to the approved estimate and its revisions. A previous amount included again can look like an import problem when the reports actually use different cut-off points. Obtain a valuation summary and test an item with movements in two periods before accepting the entire exchange.
Provide an issue the vendor can reproduce
Send a reduced sample through an agreed channel after removing unnecessary information. Include item code, expected value, actual value, both software versions and exact steps. Attach the original BC3 and reference summary rather than only a screenshot of the total. State whether the problem recurs on reimport and whether a small newly created file shows the same behaviour.
Decide when an import is acceptable
Agree rounding tolerances appropriate to the workflow and ensure they do not conceal missing items. Acceptance should cover structure, units, measurements, rates and additional concepts as well as the total. Retain the report and settings. If the final destination is an ERP, also check the mapping between BC3 codes and project cost items: a correct amount allocated to the wrong project is still incorrect information.