VAT-Inclusive vs VAT-Exclusive Prices: Getting the Direction Right

A 199.90 price tag with 19% VAT is not 199.90 + 38.00. The tag already contains the tax — adding it again double-counts. Yet "add VAT on top" remains the most common invoice mistake, and the Discount & VAT Calculator exists to make the direction explicit instead of assumed.

Two conventions, one formula each

Exclusive (B2B quotes, US sales tax): VAT is charged on the discounted net. Net 100, discount 10%, VAT 20% → net 90, VAT 18, final 108.

Inclusive (EU/TR retail tags): discount applies to the gross first, then tax is separated out of what remains. Gross 100, discount 10%, VAT 20% → discounted gross 90 → net 75, VAT 15, final 90.

The second case is where intuition fails: the natural instinct is to compute 100 − 10% = 90, then add 20% (108), then wonder why the receipt says something else. The correct extraction divides: net = gross ÷ (1 + rate).

Discounts ride first, always

In both modes the discount is applied before tax is computed — on the net in exclusive mode, on the gross in inclusive mode. That matches how receipts and invoices work: you never pay tax on money you didn't spend. The breakdown shows every step so the chain is auditable.

KDV and common rates

Turkish KDV sits at 20% for most goods (10% and 1% for reduced categories); Germany's VAT is 19%, the UK's 20%. Presets cover these, plus a zero option for comparing pre-tax pricing. An effective-change figure shows the combined discount-plus-tax delta versus the sticker price — useful for spotting "discount" marketing that the tax quietly absorbs.

Limitations

• Reverse-charge, multi-rate baskets and per-line tax rules are out of scope — this is single-rate math for one line item at a time.
• Quantity multiplies the unit figures; it does not model tiered pricing.

Pair it with the Invoice Generator for the document itself, and the Tip & Bill Splitter when the bill lands at the table.