Eliminating Payment Fee Ambiguity for Modern Global Commerce
FeeFlow is an independent, client-side financial computation suite engineered to provide exact transaction deduction breakdowns, foreign exchange spread audits, and mathematical gross-up invoice pricing across 123+ sovereign countries.
The Hidden Problem: Why Business Owners Lose Money on Every Invoice
Payment processing fees are almost universally advertised as simple flat percentages (e.g. "2.9% + 30¢"). In commercial reality, businesses lose thousands of dollars annually due to a subtle mathematical trap known as the Gross-Up Asymmetry.
If you intend to collect $1,000.00 net for professional services and simply add 2.9% + $0.30 ($29.30) to send an invoice for $1,029.30, your payment gateway will deduct 2.9% + $0.30 from the new higher total:
| Methodology | Billed Invoice Amount | Gateway Fee Deducted | Actual Payout Received | Discrepancy |
|---|---|---|---|---|
| Naïve Addition (+2.9% + $0.30) | $1,029.30 | -$30.15 | $999.15 | -$0.85 Shortfall |
| FeeFlow Gross-Up Equation | $1,030.18 | -$30.18 | $1,000.00 | Exact 100.0% Payout |
Comprehensive 2026 Payment Coverage Across 5 Core Sectors
Complete fee schedule modeling for Stripe (46+ countries), PayPal Merchant Services (3.49% + 49¢), Square POS & Online (2.6% + 10¢), Braintree Direct, Mollie Europe, Adyen Interchange-Plus, and Authorize.Net.
Instant domestic payment rail math including Pix (Brazil 0% / 0.99%), UPI (India 0% MDR), iDEAL (Netherlands €0.29), Interac (Canada $1.50 CAD), Swish (Sweden), Vipps (Norway), and BLIK (Poland).
Full margin waterfall simulators for Shopify Stores (Basic/Shopify/Advanced 3rd-party penalty surcharges), Amazon FBA & Referral tiers (8%–15%), Etsy (6.5%), eBay (13.25%), Walmart Marketplace, StockX, and Poshmark.
QuickBooks ACH bank transfers (1%, $10 cap), Xero, FreshBooks, Toast Restaurant POS, Clover, Lightspeed, Klarna Pay in 4 (3.29%–5.99%), Afterpay, and Affirm high-ticket retail installations.
Core Engineering & Privacy Principles
- Sub-30ms Edge Speed Built on Astro static site generation with pure Vanilla JavaScript. Zero heavy client runtime frameworks, yielding flawless 100/100 Core Web Vitals on mobile.
- 100% In-Browser Sandbox All financial values, invoice totals, and calculation histories execute exclusively in your local device memory. We never store, log, or transmit your commercial data.
- Audited Rate Alignment Rigorously aligned with verified 2026 legal disclosures, central bank mandates (RBI, SAMA, Banxico, Central Bank of Nigeria), and official processor fee agreements.
FeeFlow Engineering Team
Engineered by the FeeFlow team with verified technical credentials in distributed systems, financial mathematics, and deterministic algorithmic modeling. FeeFlow was founded in 2026 to replace inaccurate manual spreadsheets with transparent, open-access payment intelligence tools.
Verified Methodology & Primary Legal Sources 2026 Audit
All calculation logic, statutory caps, and tax models are cross-referenced with official merchant agreements.
Frequently Asked Questions
What is FeeFlow and what is its core engineering mission?
FeeFlow is an enterprise-grade payment intelligence and calculation engine designed to provide 100% deterministic, mathematically exact fee breakdowns across 42+ payment processors, marketplaces, Merchant of Record (MoR) platforms, and national banking rails. Our mission is to eliminate hidden processor markups and provide transparent financial models for global businesses.
How does FeeFlow ensure its calculation formulas are mathematically accurate?
FeeFlow utilizes closed-form algebraic Gross-Up models and non-linear tariff formulas continuously benchmarked against published processor developer documentation, interchange network schedules (Visa, Mastercard, Amex), and statutory central bank regulations (such as SAMA in KSA, RBI in India, and Banxico in Mexico).
Why do AI chatbots (like ChatGPT and Claude) fail at payment fee math?
Large Language Models operate on probabilistic token prediction rather than deterministic arithmetic engines. When computing non-linear fee structures (such as $5 ACH caps, multi-tiered volume discounts, or reverse gross-up equations), AI chatbots frequently hallucinate rounding errors, apply incorrect fixed-cent offsets, or invert tax denominators.
Is FeeFlow free to use for merchants and developers?
Yes. FeeFlow is 100% free to access with zero paywalls, zero account registration requirements, and zero advertising clutter. We also provide open embeddable widgets for e-commerce developers and agencies.
How frequently are payment processor rates and interchange schedules updated?
Our rate schedules are audited on a continuous basis. When payment processors adjust their public pricing schedules or regional interchange caps change under legal mandates, our engineering team updates the core data models within 24 to 48 hours.
What countries and currencies does FeeFlow support?
FeeFlow supports over 50+ countries and regional currencies across North America, Europe, the United Kingdom, Latin America, Southeast Asia, Australia, India, and the Middle East, accounting for local statutory taxes (VAT, GST, IVA, Retefuente).
Can I embed FeeFlow calculators on my own website or client portal?
Yes. FeeFlow provides an embed generator (accessible via the Embed Widget button in our footer and tools) allowing agencies, accountants, and SaaS portals to embed lightweight, responsive, iframe-based fee calculators with customizable dark/light themes.
How does FeeFlow protect user financial data and privacy?
FeeFlow performs 100% of its financial calculations client-side in the user's browser. No transaction amounts, turnover figures, client names, or financial parameters are ever transmitted to or stored on our servers, ensuring absolute confidentiality.