We do not copy the platforms' text: we summarise and link to the source. If you spot an out-of-date figure, tell us. contact@profyza.com.
GOV.UK — VAT rates ↗Reviewed on August 21, 2026 · Verified at the official source
Checked against the official source: 20% standard rate, 5% reduced rate and zero-rated supplies (0%).
Canada Revenue Agency — which GST/HST rate to charge ↗Reviewed on August 21, 2026 · Verified at the official source
Checked against the official CRA table, which publishes GST/HST and PST separately. The presets in this tool are each province’s combined rate. The CRA itself warns that the applicable rate depends on the place and type of supply.
Etsy — Fees & Payments Policy ↗Reviewed on August 21, 2026 · Verified at the official source
Confirmed the 6.5% transaction fee on the displayed price plus shipping and gift wrapping, and the $0.20 listing fee per listing.
Etsy Help — Payment Processing Fees ↗Reviewed on August 21, 2026 · Verified at the official source
Checked against the official per-country table: all eight markets in this tool match, including the domestic and international rates for Canada and Australia. The same page confirms the 6.5% transaction fee on the whole order. It also confirms this fee's base: the total sale price, including shipping and any applicable sales tax; this calculator has used that as its default base since 2026-08-21.
Etsy Help — Regulatory Operating Fee ↗Reviewed on August 21, 2026 · Verified at the official source
Checked against the official country list: Canada 0.50%, France 1.14%, Italy 0.80%, Spain 0.88% and the United Kingdom 0.48%. Germany, the United States and Australia are not on the list, so the fee does not apply there. The official base is the item price plus shipping, including gift wrap and personalization.
Etsy Help — How Etsy's Offsite Ads Work ↗Reviewed on August 21, 2026 · Verified at the official source
Checked against the official source: 15% if the shop has never made $10,000 USD or more in any consecutive 365-day period, 12% once it has, and a $100 USD cap per attributed order regardless of the shop's currency.
Amazon — selling plan pricing (Spain) ↗Reviewed on August 21, 2026 · Verified at the official source
Confirmed €0.99 per item sold and €39 per month, both excl. VAT, and that most referral fees fall between 8% and 15%.
Amazon France — selling fees ↗Reviewed on August 21, 2026 · Verified at the official source
Checked against the official pricing page: €0.99 per unit sold on the Individual plan and €39 per month, excluding VAT, on the Professional plan.
Amazon Germany — selling fees ↗Reviewed on August 21, 2026 · Verified at the official source
Checked against the official pricing page: €0.99 per unit sold on the Individual plan and €39 per month, excluding VAT, on the Professional plan.
Amazon Italy — selling fees ↗Reviewed on August 21, 2026 · Verified at the official source
Checked against the official pricing page: €0.99 per unit sold on the Individual plan and €39 per month, excluding VAT, on the Professional plan.
Google Ads — official advertising metrics glossary ↗Reviewed on September 14, 2026 · Verified at the official source
Primary provider source for the definitions of ROAS, CPA, marginal ROAS and ROI. It supports what the metrics mean; Profyza's break-even thresholds are mathematical derivations from contribution margin.
Oracle NetSuite — inventory optimization calculations ↗Reviewed on September 1, 2026 · Verified at the source
Defines safety stock as the lead-time demand standard deviation multiplied by the z-score, combining demand and lead-time variability, and the reorder point as that buffer plus lead-time demand. It rounds both up to the next whole unit, as this calculator does.
European Commission — cross-border VAT for businesses ↗Reviewed on September 2, 2026 · Verified at the source
States that buying goods for business use from a supplier outside the EU generally means paying VAT at the point of import, and that a business making taxed sales usually can deduct it later on its VAT return. The page itself warns that important exceptions exist, and national rules apply on top. That is why only the portion whose deductibility you have confirmed should be entered as recoverable tax.
Shopify — break-even analysis and contribution margin ↗Reviewed on September 1, 2026 · Verified at the source
Defines contribution margin per unit as selling price minus variable cost per unit, and break-even units as fixed costs divided by that contribution. It separates fixed from variable costs, the distinction these calculators rest on.
Shopify — CAC payback period ↗Reviewed on September 1, 2026 · Verified at the source
Defines payback as acquisition cost divided by average monthly gross profit per customer, expressed in months. This calculator uses monthly contribution instead, which is stricter than gross profit because it deducts every variable cost.
Shopify — ecommerce customer acquisition and cost per customer ↗Reviewed on September 1, 2026 · Verified at the source
Computes acquisition cost as total sales and marketing spend divided by new customers, and describes contribution margin — revenue minus variable costs per order — as what is available to offset that acquisition.
Shopify — shipping strategies and minimum order threshold ↗Reviewed on September 1, 2026 · Verified at the source
Recommends setting the free-shipping threshold from average order value and warns that free shipping is not free: it is either absorbed into price or limited to products with enough margin.
Shopify — product bundling strategies and bundle discounts ↗Reviewed on September 1, 2026 · Verified at the source
Describes bundle types and pricing approaches, and warns that a badly designed bundle can cut profit. It does not quantify how much extra volume offsets a discount, which is exactly what this tool works out.
Shopify — stockouts: causes and consequences ↗Reviewed on September 1, 2026 · Verified at the source
Describes the consequences of running out of stock and offers an estimate that treats all unmet demand as lost. This calculator is more conservative: it asks what share is actually lost, because some demand waits or buys something else.
QuickBooks — inventory carrying cost ↗Reviewed on September 2, 2026 · Verified at the source
Groups inventory carrying cost into four families — capital costs, inventory service costs, inventory risk costs and storage space costs — and gives the formula as inventory holding cost divided by total inventory value, multiplied by one hundred.
Shopify — inventory carrying costs and how to calculate them ↗Reviewed on September 2, 2026 · Verified at the source
Gives the formula as the sum of holding costs divided by total inventory value, times one hundred, and groups those costs into capital, storage, service — insurance and taxes — and risk — depreciation, shrinkage and spoilage. Those are the same groups broken out here as seven annual amounts.
Wall Street Prep — cash conversion cycle and its components ↗Reviewed on September 1, 2026 · Verified at the source
Gives the cycle as DIO plus DSO minus DPO, with inventory and payables over cost of goods sold and receivables over revenue, all multiplied by the days in the period. It also explains why a negative cycle is a source of cash.