Waste, tax, and contingency are different inputs

Planning workflow

1. Choose waste by material, layout, product, skill, and reuse plan.
2. Round the resulting purchase quantity to actual package constraints.
3. Apply tax only after confirming jurisdiction, exemptions, and taxable categories.
4. Set design and construction contingencies according to estimate maturity and named risks.

Formula or decision logic

Purchase quantity = raw quantity x (1 + waste rate), then package-round. Tax = taxable subtotal x tax rate. Contingency = defined eligible cost base x contingency rate. The order matters, and percentages must show their base; adding all rates together and multiplying once is usually not equivalent.

Worked planning example

A raw flooring need of 1,000 sq ft with 8% waste becomes 1,080 sq ft before cartons. At $4 per sq ft, material subtotal is $4,320. A hypothetical 6% tax on that base is $259.20. A separate contingency must state whether it applies to materials, all construction, or another subtotal.

Limitations and review boundary

• Waste is product- and layout-specific.
• Tax treatment is jurisdiction- and transaction-specific.
• Contingency does not replace investigation, design, insurance, or contractual risk allocation.

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