Buy Now Pay Later Fee Impact Planner methodology

standardContributionPerOrderExTax = pre-fee contribution − standard fee

bnplContributionPerOrderExTax = pre-fee contribution − BNPL fee

standardPeriodContributionExTax = visitors × baseline conversion × standard contribution

bnplPeriodContributionExTax = visitors × BNPL conversion × BNPL contribution

contributionDeltaExTax = BNPL period contribution − standard period contribution

requiredBnplConversionRate = baseline conversion × standard contribution / BNPL contribution; unreachable above 100%

Money inputs and outputs use the currency selected in the scenario without changing the canonical methodology. Rates, margins, utilisation and buffers are entered as percentages and converted to decimal values for calculation.

• Average order value must be finite and greater than zero; pre-fee contribution and fixed fees must be finite and non-negative.
• Standard and BNPL fee rates must be at least 0% and strictly below 100%; both conversion rates must be between 0% and 100% inclusive.
• Visitors must be a whole, non-negative number; negative calculated contribution remains visible evidence.
• Required BNPL conversion is unreachable, not infinite or a numeric sentinel, when BNPL contribution per order is zero or negative.
• All values must be finite and inside the visible validation boundaries.
• Rates are entered as percentages and calculations retain decimal precision.
• Money uses one consistent ex-tax currency and planning period.

• All standard-payment and BNPL fee defaults are neutral zeroes and must be replaced with the user’s own contract values.
• No named provider, current commercial fee or provider conversion claim is embedded.
• Provider fees, exchange rates, return behaviour and operating performance are user-entered scenarios.
• No provider plan, jurisdiction, tax rate or market benchmark is embedded.
• The engine retains full precision and display formatting never feeds back into calculation.

This planner has no current policy-data dependency. Its commercial assumptions are user supplied. Registered family-level regression suites exercise the shared business-logic engine and worked-result reconciliation.

• The model does not forecast demand, provider changes, exchange rates or operational performance.
• It does not replace accounting, tax, legal or financial advice.
• The conversion uplift is a user scenario rather than a provider claim; a required conversion above 100% is shown as unreachable. Merchant eligibility, settlement timing, refunds, disputes, consumer-credit rules and tax are outside the model.

This is educational decision support, not tax, accounting, legal or financial advice. Check the treatment of your actual transactions under the rules that apply to your business and seek qualified advice where appropriate.

Registered family-level suites test formula invariants and example reconciliation; the release ledger records that coverage without claiming a separate oracle for every line of public copy. There is no official threshold or benchmark to refresh for this planner. Commercial inputs remain user-supplied because they vary by business and contract.

1. 2026-07-16: Initial public release of the Buy Now Pay Later Fee Impact planner and methodology.