An illegal extension or a missing occupancy certificate can block a mortgage, a sale or even lead to a demolition order. How to spot it and what to check by country.
A villa with a terrace that was added later, a flat whose attic was converted into a bedroom, an apartment rented to tourists without a licence: in many markets this is common, and the buyer inherits the problem with the keys. This guide explains what the risk is, how to find it before you pay, and what the consequences can be.
What buyers fear
Buyers fear three things: that the authorities will order part of the building to be demolished or fined, that they will not be able to sell later or take a mortgage, and that what looks like a normal title in the registry hides a building that was never legally completed. The fear is justified in some markets and exaggerated in others, and it depends on what exactly is missing.
What the risk really is
Three different situations are often mixed together.
- Building without a permit, or beyond the permit (extra floor, enlarged footprint, closed terrace). This is an administrative offence; depending on the country and the age of the building it can be legalised, fined, time-barred or demolished.
- A building that is lawful but has no final paperwork (no occupancy or habitation certificate, no completion act). This often blocks utility contracts, mortgages and registration, even though the structure itself is not illegal.
- Unlicensed use, for example short-term letting without the required tourist licence or use of a commercial unit as housing. The building is fine, the use is not.
What is and is not protected: a clean entry in the land registry does not always prove that the building matches the permit. In several systems the registry records ownership, while the match between the building and its permits is checked by a different body (the municipality or the cadastre). Do not treat the registry extract alone as proof.
How it works by country
Spain. A new building is registered by a declaration of new works (declaración de obra nueva), which normally requires the building licence, the architect's end-of-works certificate and, where the regional law requires it, the first occupation licence (licencia de primera ocupación). Older buildings can be registered based on their age under state rules, but the details differ by region. The cédula de habitabilidad or equivalent is requested in some regions for utility contracts and sales. Always ask for the nota simple from the property registry and check whether the registered area and the built area match. See Spain resale property checklist.
Italy. Italian practice separates two checks: conformità urbanistica (the building matches the permits) and conformità catastale (the cadastral plan matches reality). They are independent; a property can be updated in the cadastre and still be unlawful under planning rules. Reported case law treats a missing cadastral conformity statement in the deed as a ground for nullity. Past amnesties (condono) and later sanatoria procedures must be mentioned in the deed. Ask the notary and a geometra to confirm both. See Italy resale property checklist.
Portugal. The licença de utilização certifies that the building may be used for its stated purpose. Reported 2023-2024 simplification measures changed whether it must be shown at the deed, and a further change was reported for late 2026, so ask the notary what is required now. Do not skip the check of the caderneta predial against the registry (certidão predial), and confirm that the area and use match. See Portugal resale property checklist.
Greece. Law 4495/2017 created a regime for legalising unauthorised buildings and changes of use, subject to declarations, fines and an engineer's work; deadlines have been extended repeatedly and are reported to run to the end of 2026 for some procedures, with the Building Identity for the oldest category reported to run until 2028. A seller of an unlicensed building usually needs an engineer to confirm legal status before the sale. See Greece resale property checklist.
Cyprus. The best-known problem is title deeds: buyers who paid a developer and could not get the title because the land was mortgaged or planning papers were missing. Reported Law 110(I)/2025 created a new framework for such cases and administrative fines for sellers and mortgagee banks were reported from February 2026. Always check whether title deeds can be issued, and whether there is a bank charge over the plot. See Cyprus resale property checklist.
Bulgaria. The key document for a new building is the Act 16 (certificate of completion and occupation); earlier stages such as Act 14 and Act 15 describe a rough shell or a finished building without final acceptance. A building without Act 16 can be hard to connect to utilities and to sell. See Bulgaria resale property checklist.
Turkey. Every completed building needs an occupancy permit (iskan, yapı kullanma izin belgesi) before it is lawfully occupied and connected to permanent utilities. Check that the title deed (tapu) matches the actual unit and that the iskan has been issued, especially when buying from a developer.
Montenegro. A large number of buildings were built without permits. A new law on legalisation reportedly came into force on 1 August 2025, and brokers report that processing is slow, with only a small share of the many applications decided. A building in the process of legalisation is not the same as a legalised building. See Montenegro resale property checklist.
Consequences
- Financing: banks usually lend only on properties with clear title and valid permits; an illegal extension can reduce the loan or block it.
- Sale: a later buyer, or their bank and notary, will ask for the same papers. The problem passes on to you in the form of a lower price or a failed sale.
- Penalties: fines, orders to restore the original state, in serious cases demolition at the owner's cost. The actual risk depends on the age of the work, the zone (protected or coastal areas are stricter) and local enforcement.
- Insurance and utilities: some insurers and utility companies require occupancy papers.
- Rental: tourist use without a licence can bring fines and platform delistings. See short-term rental rules.
Due-diligence checklist
- Get the registry extract and compare the registered area, floors and use with the real building and with the advertisement.
- Ask for the building permit, the end-of-works or completion document and the occupancy or habitation certificate.
- Ask for the cadastral or planning certificate and for any pending notices, fines or legalisation files at the municipality.
- Have a local technician (architect, engineer, geometra) compare the permit drawings with the building on site. See technical survey before buying property abroad.
- Check the licence for any tourist or commercial use that is part of the price.
- Make the contract condition the delivery of the missing papers, with a retention of part of the price until they are delivered.
- Ask about the community of owners: unpaid charges and unapproved changes to common parts.
- Never accept verbal assurances such as "everything is fine, it is normal here". See also double sales and hidden debts and how to verify a developer abroad.
When to involve a lawyer or notary
Involve an independent lawyer before any reservation payment if the papers are incomplete, if the building was extended, or if you are buying a house, ruin or plot. For land and ruins see buying land abroad: plots, zoning and permits. To choose the right professional, see notary or lawyer: who do you need abroad. Official information on EU property systems is available on the e-Justice portal.
FAQ
Can an illegal extension be legalised? In many countries yes, under conditions and for a fee or fine, but not always. Legalisation depends on the zone, the date of the work and compliance with safety rules. Ask a local technician before you sign.
Does the registry extract prove the building is legal? Not by itself. It shows ownership and registered data, while compliance with permits is checked at the municipality or the cadastre.
Who pays for legalisation? It is negotiated. It is normally better for the seller to legalise before the deed, or for the price to be reduced and part of the money retained until completion.
Can the authorities demolish a building years after it was built? In some countries the time limit for enforcement runs out, in others it does not, and protected zones are treated more strictly. This is a point for a local lawyer.
Is a new-build safe? Not automatically. Check the permit, the completion certificate and the developer. See snagging and handover.
How we help
We are a trilingual platform that finds properties and coordinates independent local lawyers and technicians who check the permits and the registries for your specific property. This text is informational and is not legal, tax or investment advice; rules differ by country and region, so verify the current requirements with your lawyer and the competent authorities.