Guide · Money and risk

The hidden long-term costs — what the listing doesn't highlight

Most surprises in a home purchase aren't the price itself. They're the bills that arrive years after you take over — and rarely appear clearly in the sales particulars. Here are five we run into again and again in our test analyses, and how to find them yourself.

Test analysis before launchThe findings in this article come from test analyses we did on real properties for sale, before launching BoligCheck — not paid client reports.
01

The decommissioned oil tank in the garden

In older houses we often come across an emptied and decommissioned oil tank — an old, buried tank that's been sealed off but not removed. Even an empty tank can corrode over time, and in some cases the rules can require actual removal, not just decommissioning.

How to check: the tank is typically listed in the property data report (ejendomsdatarapport). Ask for documentation of the decommissioning date, and ask the municipality whether physical removal is required.

What it costs: simple decommissioning (the tank is sealed and filled, but stays in the ground) typically costs 2,500–8,000 kr. Full physical removal (excavation) typically costs 15,000–30,000 kr, depending on the tank's size, location, and whether soil samples are required.

Seen in a test analysis we did before launch: a detached house where the property data report stated an emptied and decommissioned tank, with no date or status mentioned in the listing itself.
02

Easements with "financial obligations"

On plots from the first half of the 1900s we regularly see a registered easement (servitut) with the text "contains financial obligations, see deed". This can mean payment obligations for a road, utilities or sewer — and it refers to a deed almost no one actually reads.

How to check: request the full deed document (a title registry extract), not just the line in the sales particulars. Don't treat it as a formality until you've read it.

Seen in two different test analyses we did before launch: the exact same wording, with deeds from 1926 and 1930 respectively — a pattern, not a one-off, which is exactly why it's worth checking every time.
03

Private water supply — not the municipal mains

In the countryside we see homes with a "private water supply system" — water from your own borehole or well, not the municipal waterworks. That means you're responsible for the pump, periodic water-quality testing and potential future repair or new-borehole costs.

How to check: ask about the system's age, the pump's condition, and when the water quality was last tested.

Seen in a test analysis we did before launch: a rural house where the water supply was private — an ongoing cost and responsibility that doesn't exist with municipal water.
04

Upcoming separate sewer requirements

Many older houses share one drain for rainwater and wastewater. Municipalities increasingly require separate sewer systems (separatkloakering) — splitting the two — and when the requirement lands, the bill lands on the property owner. The sales particulars sometimes mention it as something the agent considers "not their concern", i.e. outside their responsibility.

How to check: ask the municipality whether there's a timeline for separate sewer requirements on that specific road.

Seen in a test analysis we did before launch: the sales particulars mentioned the requirement directly, but explicitly disclaimed responsibility for the future cost.
05

"Newly renovated" — but not in BBR

A home is marketed as fully renovated, but the official BBR building register shows "year of significant renovation: not stated". Updating BBR after a renovation is the owner's responsibility and sometimes gets postponed. It's not a problem in itself — but it can affect future registration and certain tax matters, and an "end-to-end" renovated impression can in practice turn out to be partial.

How to check: compare the listing's stated renovation year with the BBR registration, and ask whether a BBR update has been submitted.

Seen in two test analyses we did before launch: the marketing's renovation year didn't match BBR — the same pattern in two different houses.
What all five have in commonNone of them is necessarily a red flag in itself. But they share one trait: they don't cost anything today — they show up as a bill years after you take over. That's why they're easy to overlook when you're only looking at price and photos.

Sources and further reading: BBR · Tinglysning.dk (title registration) · The Danish Environmental Protection Agency (oil tanks)

We find the hidden costs before you bid

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Also read: Ejerudgift — what the listing doesn't tell you · How to read the condition report · Andelsbolig — the low price doesn't tell the whole story