Keep source figures and terms separate
Identify which values come from the weekly return and which come from an agreement. Record the reporting period and the approved version of the terms. Do not turn a missing term into a default assumption.
Choose meaningful test weeks
Include a normal week and cases that change the result: a different performance count, a minimum applying, missing information or a corrected source figure. The relevant cases depend on your agreements.
Compare each component
Check the inputs, individual amounts, rounding and final total against completed examples. If a result differs, trace the difference to a source or rule before treating either the software or spreadsheet as correct.
Agree the review and output
Decide who approves the calculation, what evidence they need and what happens after review. Calculation, approval and payment are separate steps. No example formula should be treated as a rule for every production.