The VAT math in your invoice, checked with one number
Two freelancers invoice the same client the same €1,000 project. One bills €1,240, the other bills €1,200, and both are right. The difference is whether VAT was added on top of a net price or extracted from a gross price, and mixing the two up is the most common spreadsheet error in European invoicing.
Net, gross, and the direction of the math
When you quote a net price, VAT goes on top: at 20%, a €1,000 net invoice becomes €1,200 gross, and the €200 of VAT is what you owe the tax authority. When a price already includes VAT, the tax has to be pulled back out: €1,200 gross at 20% means net of €1,000 and €200 of VAT, because the gross figure is 120% of the net.
The trap is the mental shortcut "just take 20% off." Taking 20% off €1,200 leaves €960, which is wrong. The correct factor is net = gross / (1 + rate). A VAT calculator does either direction once you pick which number you started from, and it is worth checking a hand calculation against it once, because the difference between €960 and €1,000 is exactly the kind of error nobody catches until the accountant does.
Which price is which depends on your audience. B2B quotes are usually net plus VAT. Consumer-facing prices in shops and SaaS pricing pages are gross. A single landing page that shows both without labels will generate support tickets.
Rates that look the same and are not
The rate is the easy part; the classification is what costs money. Most countries have a standard rate plus reduced rates that depend on the good or service: food, books, and children's clothing often carry reduced rates; digital services sold to consumers usually take the customer's country rate, not yours; cross-border B2B within the EU may reverse the charge entirely. The same invoice data can produce three defensible totals with three different rate decisions, which is why the rate is a business decision first and an arithmetic one second.
Why the totals differ by a cent
The classic invoice mystery: line items that each round cleanly, and a total that does not match their sum. This happens when each line's VAT is rounded separately and then summed, versus VAT computed on the rounded subtotal. Both are accepted practice, but they disagree by a cent here and there.
- Line 1: €33.33 net, 20% VAT is €6.666 → €6.67
- Line 2: €33.33 net, 20% VAT is €6.666 → €6.67
- Line 3: €33.34 net, 20% VAT is €6.668 → €6.67
Sum of rounded line VAT: €20.01. VAT on the net total €100.00: €20.00. One cent, two correct answers. Invoice formats that total the line VAT and invoice systems that recalculate from the subtotal will keep reporting different numbers until everyone agrees on one method. Knowing which camp your accounting tool sits in turns the argument into a setting.
Rounding rules worth setting once
Pick your rules early and write them into the invoice template: round per line or per invoice, banker's rounding or round-half-up, and two decimals everywhere except unit prices on line items. Changing the method later means old and new invoices disagree with each other, and auditors ask about inconsistencies, not intentions.
Reverse charges and the zero that is not zero
When an invoice legitimately shows 0% VAT with a reverse-charge note, the math looks like any other invoice but the compliance layer is different: no VAT charged means the buyer self-accounts for it in their own country. The numbers still need the same care, because the net amount is what flows into both companies' VAT returns. A percentage calculator covers the plain arithmetic, but the reverse-charge case has no tax to calculate at all, just a note that has to be there.
VAT is not complicated. It is specific. The formulas are two lines of arithmetic; the mistakes come from the assumptions around them, which take one careful look to get right and one audit to regret.