Primary sources first
Marketplace fee pages, legal policies, seller help centers, and payment-provider rate tables are the preferred sources. Third-party coverage can alert us to a change but does not set a calculator default by itself.
Reviewed dates and update triggers
Rate-sensitive calculators display when their source was reviewed. Editorial monitoring looks for policy changes, but a human-verifiable primary source, formula update, tests, and production QA are required before publication.
Formula testing
Calculations are tested against representative transactions, flat-fee thresholds, category tiers, zero-cost cases, target-pricing behavior, and invalid inputs. Browser tests confirm live recalculation on desktop and mobile.
AI assistance
AI tools may assist with research organization, drafting, code, or quality checks. They do not replace source verification. No fee, date, platform rule, or claim is published solely because a model produced it.
Corrections
Substantive corrections are prioritized. Updated pages receive a new reviewed date, and formula changes must pass the same tests as the original release. Correction reports can be sent through the contact page.
Commercial independence
Advertising, affiliate relationships, or sponsorships do not buy a favorable calculation, hidden fee assumption, or altered conclusion. Sponsored material will be labeled.