VAT / sales tax
Gross to net is a division, not a multiplication. The three figures always add back up.
- Runs
- In this tab
- Data sent
- None
- Rounding
- Once, at the end
- Also in
- The Chrome extension
VAT / sales tax, worked
Showing a worked example — type over it
Result
Where these numbers come from.
Negatives are parenthesised because that is what a statement does. The rest is four promises.
Minor units, never floats
Amounts are integers in the currency's smallest unit, end to end. A float never touches a cent.
Rounded once
Rounded once, at the end — never per operand, which is how a split stops summing to the whole.
Unit tested
The arithmetic lives in one unit-tested module, shared without reimplementation with the extension.
No network
There is no request to make. What you type stays in this tab and is gone when you close it.
More in money maths
- Margin & markupThey are not the same number, and confusing them is how a price list quietly loses money.
- FX conversion & gain/lossThe rate is the one in your policy, so you type it. No live rate, no network call, no stale surprise.
- Penny-exact allocationSplit 100.00 three ways and get 33.34 / 33.33 / 33.33 — never a cent left in suspense.
- NPV, IRR & XIRRIRR by bisection, so a sign-change-heavy series does not converge on a confident wrong answer.
- Effective vs nominal rate12% compounded monthly is 12.68%. That difference is the covenant you either pass or fail.
Read it in context
- Founder guide · 4 minSales tax nexus for startups: when you owe tax in a stateSince Wayfair, selling into a state can create a sales tax obligation. How economic nexus works, why SaaS is taxable in some states and when to register.
- Founder guide · 6 minRegistering in a new state: remote hires and nexusA remote hire or nexus in a new state means foreign qualification, payroll tax accounts and maybe a sales tax permit. What to register, in what order.
The same number, elsewhere.
A calculator answers the question once. These carry the answer into a product, name what it computed, and argue the method.
- ComponentInvoiceFormWith the revenue-recognition preview per line.
- ComponentBillFormPer-line coding, required evidence, discount ROI surfaced.
- ComponentCheckoutSummaryItemized total with fees and tax.
- TermInvoiceA claim on a customer
- TermBillA claim against us
- TermSales tax nexusThe connection with a state that obliges a seller to collect its sales tax — physical presence, or economic nexus from sales into the state above a threshold (commonly $100,000) since South Dakota v. Wayfair (2018)
- DocOrder to cash (AR)The complete receivables stack: quote → order → fulfilment → invoice → collection → cash application → revenue.
- EntryJournal entry for sales tax collectedWhen a taxable sale is made, debit Cash or Accounts receivable for the total charged, credit Revenue for the price and credit Sales tax payable for the tax. When the return is filed, debit Sales tax payable and credit Cash.
- DocCurrency decimal placesHow many decimals each ISO 4217 code is stored at — JPY 0, USD 2, KWD 3.