Deduct known non-service costs
Start with the approved budget and remove any costs that must be paid separately. Use the remaining amount for the service calculation. Keep those deductions visible so the client can understand why the quantity is lower than a headline rate suggests.
Apply the correct unit rate
For a per-thousand service, divide the usable budget by the rate and multiply by one thousand. Round down to a permitted quantity increment. Then confirm the result still meets the service minimum and any maximum order restriction.
Stop at the approved scope
A remaining balance does not authorize an extra action or a different target. Save the final quantity and expected charge for approval. Recalculate if the rate changes before purchase, rather than letting an old budget silently create an overrun.
Decision checklist
| Decision | What to check |
|---|---|
| Budget | Approved amount |
| Usable | After known costs |
| Quantity | Permitted rounded-down amount |
Worked example
With a hypothetical $10 usable budget and a $3 rate per thousand, the arithmetic limit is 3,333.33 units. If orders require increments of 100, 3,300 units cost $9.90, leaving $0.10 unused.
Example figures explain the decision; they are not current prices or promised results.