How it works · one real quarter

Twelve days in October, with Maya

Maya is a freelance designer in Amsterdam — ZZP since 2024, about €72.000 turnover this year. It's mid-October: Q3 closed on 30 September, and the btw-aangifte is due by 31 October. Here is the whole thing, start to closed drawer.

Figures: tax year 2026 · estimates
01

A calm email, in time

Kwartaal writes when there's something to do — not before, not breathlessly. Twelve days out is enough for a 25-minute job.

Kwartaalpost@kwartaal.nlMon 19 Oct, 08:30
Q3 btw — due by 31 October (12 days)

Hi Maya,

Q3 closed on 30 September. Your checklist is ready — the invoices and receipts you added during the quarter are already in it, so expect about 25 minutes.

Current estimate: you'll owe around €3.500. You've set aside €2.940 so far.

Open the Q3 checklist
02

Four steps, not forty

The checklist opens with the quarter's work already gathered. Each step confirms something and echoes the number it produced — never a one-way door.

✓Income confirmed· €20.000,00 · btw €4.140,00Edit
02
Confirm expenses with reclaimable btw
4 expenses · voorbelasting €610,00 so far
03Check the numbers against the formafter step 2
04File it, pay it, close the drawerafter step 3
03

The mirror — every number, explained

Before Maya types anything into Mijn Belastingdienst, Kwartaal shows the same numbers the form will ask for — and why each one is what it is.

Q3 2026 · btw-aangifteestimate
Btw you received on Q3 invoices€4.140,00
Btw you paid on costs — −€610,00
You owe for Q3€3.530,00
Why this number
You invoiced €20.000 this quarter and collected 21% btw on most of it. You paid €610 of btw on a desk, software, and hardware. The difference passes through you to the Belastingdienst — it was never your money, which is why Kwartaal had you set it aside as you went.
04

The handoff — rubriek by rubriek

Mijn Belastingdienst asks for numbers by . Kwartaal lays them out in the form's own order, ready to copy — the typing takes five minutes.

RubriekWhat the form calls itYour number
1aLeveringen belast met 21%€4.095
1bLeveringen belast met 9%€45
5bVoorbelasting€610
5cTe betalen€3.530
Copy the numbersOpens Mijn Belastingdienst in a new tab — you file, Kwartaal waits.
05

Two acts: filed, then paid

Filing and paying are separate deadlines in real life, so they're separate confirmations here. Each one states its consequence.

✓I filed itThe aangifte is in. One thing left: the payment itself.
✓I paid it€3.530,00 with the payment reference — done means done.
06

The drawer closes

No confetti, no streak. The quarter settles into the year with a small, satisfying weight — and stays in the Vault for seven years.

✓
Q3 is closed.
Filed and paid on 22 October 2026 · 1a €4.095 · 1b €45 · 5b €610 · 5c €3.530 · Q4 opens 1 January.

Your Q4 could close like this.

The first quarter is free — no card, full access until the drawer closes.

Start free