VAT Calculator

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Calculation basis:

{{ basisMeta.amountLabel }}:

Enter one unit's amount with no more than two decimal places.

VAT rate:

Use 0% through 100%; VAT-only recovery requires a positive rate.

Invoice currency:

Choose the source document's denomination; values are not converted.

Quantity:

Enter a whole number from 1 through 1,000.

units

Rounding scope:

Match the same boundary used by the invoice or point-of-sale system.

Cent policy:

Nearest cent is the neutral audit default; use down or up only to match a known rule.

Rate shortcut:

Use an anchor as a typing shortcut, then verify the transaction's rate separately.

Scenario label:

For example, Quote 1042 or Quarter-end invoice.

Display precision:

This presentation preference leaves all posted values unchanged.

Line	Per unit	Invoice total	Copy
{{ row.line }}	{{ row.unit }}	{{ row.invoice }}

Priority	Check	Current evidence	Next action	Copy
{{ row.priority }}	{{ row.check }}	{{ row.evidence }}	{{ row.action }}

The chart renderer is unavailable. The VAT Receipt remains usable.

The chart renderer is unavailable. The receipt and review remain usable.

The same sale can be described by three linked amounts. Net is the price before value added tax (VAT), VAT is the tax amount, and gross is the amount including VAT. When any two of the net amount, gross amount, VAT amount, and rate are known, the missing values can usually be reconstructed.

The calculation route depends on which amount appears on the source document. Adding VAT to a net price uses the rate directly. Extracting VAT from a gross price uses the VAT fraction, because the tax is already inside the total. At a 20% rate, VAT is 20/120, or one-sixth, of gross rather than 20% of gross.

Net: The taxable amount before VAT.
VAT: The tax calculated at the confirmed transaction rate.
Gross: Net plus VAT.
VAT fraction: Rate divided by 100 plus the rate, used to extract VAT from a tax-inclusive amount.

Rounding can create a real invoice difference. Rounding VAT for each unit and then multiplying may not match calculating VAT for the extended invoice amount and rounding once. A point-of-sale system, supplier invoice, and accounting system can disagree by a cent even when all use the same rate.

The rate itself is a legal and factual input, not an arithmetic result. It can depend on jurisdiction, supply category, customer status, place of supply, and effective date. Rate shortcuts are convenient anchors only. Confirm the rate and the required rounding method before posting, filing, or reclaiming VAT.

How to Use This Tool:

Match the calculation basis and rounding boundary to the invoice or point-of-sale record you are checking.

Choose Calculation basis: net before VAT, gross including VAT, or the VAT amount alone. Enter the matching one-unit amount with no more than two decimals.
Enter VAT rate and select the source document's currency. Currency changes the denomination only; it does not convert values or determine the rate.
Enter Quantity, then choose whether to round invoice totals or each unit first. Keep Nearest cent unless a known accounting rule requires rounding down or up.
Review VAT Receipt for net, VAT, and gross totals. Use VAT Actions to compare the alternate rounding scope and confirm the rate, basis, and cent policy.

Interpreting Results:

The headline changes with the selected basis: net input emphasizes VAT added, gross input emphasizes VAT extracted, and VAT-only input emphasizes recovered net. The VAT Receipt remains the reconciliation point because it shows unit and invoice totals together.

Check VAT Actions whenever the alternate rounding amount differs. A nonzero delta does not automatically mean either calculation is wrong; it means the posting boundary matters. Match the source system's line, unit, or invoice method and use directional rounding only when the applicable rule permits it.

Technical Details:

Amounts are parsed into integer minor units and rates into hundredths of a percentage point before calculation. Rational arithmetic preserves the exact fraction until the selected cent boundary, avoiding binary floating-point drift in posted values.

Formula Core

The three bases use related equations but solve for different unknowns.

\begin{aligned} VAT from net & = Net \times \frac{r}{100} \\ Gross & = Net + VAT \\ VAT from gross & = Gross \times \frac{r}{100 + r} \\ Net from VAT & = VAT \times \frac{100}{r} \end{aligned}

r is the entered percentage rate. VAT-only recovery requires r greater than zero. At zero rate, net and gross remain equal and VAT is zero.

Rounding Rule Core

VAT posting and rounding rules
Setting	Posting rule
Invoice-total rounding	Multiply the exact net and VAT fractions by quantity, then round the invoice net and invoice VAT independently to the selected cent policy.
Per-unit rounding	Round one unit's net and VAT independently, add them for unit gross, then multiply each posted unit amount by quantity.
Nearest cent	Fractional minor units below 0.5 round down; 0.5 and above round up.
Round down	Discard the fractional minor unit at the selected boundary.
Round up	Raise any positive fractional minor unit to the next cent.

Net and VAT are rounded independently, and gross is their sum. The alternate result repeats the same exact calculation under the other scope so the VAT and gross deltas isolate the effect of rounding boundary alone.

Inputs accept amounts from 0.00 through 1,000,000.00, VAT rates from 0.00% through 100.00%, and whole-number quantities from 1 through 1,000. Amount and rate inputs accept at most two decimal places. Display precision changes presentation only; posted-cent values remain unchanged.

The rate sweep holds the current unit net amount, quantity, rounding scope, and cent policy constant while recalculating VAT and gross across the built-in anchor rates plus the current rate. It compares arithmetic effects and does not identify a legally applicable rate.

Accuracy Notes:

VAT arithmetic can be exact while the transaction treatment is wrong. Confirm the jurisdiction, supply category, effective date, tax point, and source-document rounding rule separately.

Rate shortcuts do not assign a country or product category.
Currency selection does not perform foreign-exchange conversion or satisfy local reporting-currency rules.
Identical-unit quantity is assumed. Mixed rates, discounts, shipping, partial exemption, reverse charge, and mixed supplies need line-by-line treatment outside this calculation.
Directional cent policies are available for reconciliation, but their legal use depends on the relevant tax authority and accounting context.

Worked Examples:

Small units expose the rounding boundary

Three units at a net price of £0.03 and a 20% rate produce exact VAT of £0.006 per unit. Nearest-cent per-unit rounding posts £0.01 VAT on each unit, or £0.03 total. Invoice-total rounding applies 20% to £0.09 and rounds £0.018 to £0.02. The one-cent difference comes from when rounding occurs, not from a different rate.

References:

VAT guide (VAT Notice 700), HM Revenue & Customs.
VAT Rates, European Commission.