Distinguish margin from markup
Margin uses selling price as its denominator; markup uses cost. With a unit cost of 120 and a target margin of 25%, the pre-tax selling price is 160: cost divided by one minus the margin fraction. A 25% markup produces 150 instead. Label the method beside the input and state which costs the calculation includes.
Scope every change
A price can apply to a product, customer group, location, or date range. Display that scope before asking for approval. Define how overlapping promotions interact and whether discounts can stack. Taxes, currency conversion, shipping, and contract terms require separate rules; a basic margin calculator should not imply it has handled those considerations.
Preview the consequences
Show the current value, proposed value, and effective date together. Let reviewers inspect a sample of affected items before publishing a bulk change. Reject values outside agreed limits and require a reason for exceptions. Use server-side validation for production systems even when the browser already validates the same fields.
Keep a recoverable history
Record who proposed, approved, and published a change. Preserve the previous price and the rule that produced the new one. A reversal may need its own effective date rather than overwriting history. Test boundary cases such as zero cost, rounding, duplicate submissions, and a promotion ending while an order is being prepared.
A planning guide. The right implementation depends on your system and requirements.
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