Calculate at full precision
Multiply the quoted rate by the requested quantity using the correct billing basis. Keep more decimal places in the calculation than you show in a customer-facing estimate. Rounding the rate first can create a different result across many small orders.
Check the documented charge
The panel's final charge may use a stated precision or minimum charge. Compare your calculation with that amount before submitting. If the difference is unexplained, ask for the applicable rule rather than assuming the lowest displayed decimal is binding.
Reconcile batches carefully
Add actual order charges when reviewing a completed batch. Summing individually rounded estimates can differ from rounding one combined estimate. Preserve enough detail to identify whether the discrepancy comes from arithmetic, rate changes, or a separate fee.
Decision checklist
| Decision | What to check |
|---|---|
| Rate | Unrounded quoted value |
| Charge | Final displayed deduction |
| Batch | Sum of actual charges |
Worked example
At a hypothetical rate of $0.37 per thousand, 125 units calculate to $0.04625. Rounding that estimate to two decimals gives $0.05. Ten actual charges of $0.05 total $0.50, not $0.46.
Example figures explain the decision; they are not current prices or promised results.