Guides
How to use the site, where the figures come from, and how we calculate and keep everything up to date.
Help
Step by step, for when something on your phone or computer doesn't work right away.
- The 30% ruling (expat scheme) explainedWhat the 30% ruling is, how the tax-free amount is determined, what changes in 2027 and which points are not officially confirmed.
- Sharing your locationWhy Sumish asks for your location, what we do with it and how to switch it on on iPhone, Android, Windows or Mac. Or just type a town.
Data
Which data we use, who publishes it and how often we fetch it.
- CBS figures on neighbourhoods and municipalitiesWhere the figures for neighbourhoods, districts and municipalities come from, which year they are from and why CBS sometimes keeps a figure secret.
- Current prices in the calculatorsWhich price is already filled in for fuel, charging and energy, which CBS series it comes from and what happens when it is not available.
- Maps and addresses: PDOK and the KadasterWhere the map, the addresses and the postcodes on Sumish come from, and why the map runs through our own server and passes nothing on about you.
How we work
How we calculate, check and keep the tools up to date.
- Allowances: assessment income, assets and advance paymentWhat the Benefits department means by assessment income, allowance partner and assets, and how the advance, final determination and repayment work.
- How our calculators work and how reliable a result isHow a result comes about, what indication or worked example means, how we round and how we check the formulas.
- How we keep everything currentWhich data updates itself, which rates we check by hand every year and what Last reviewed means on a tool.
- How we make sure data stays current and checkedWhat you can see of the review date, the values with an effective date and the data that updates itself, and what we do when a source goes quiet.