The ley del mono in Chile: the two regimes, the requirements and the running deadline

Quick answer: the ley del mono, the simplified regularisation act, is law 20.898, and it sets out a simplified procedure for regularising homes and extensions that were built without a permit. It has two regimes: up to 90 square metres with a tax appraisal of up to 1,000 unidades de fomento, and up to 140 square metres with an appraisal of up to 2,000. In both, the building must be from before 4 February 2016. Law 21.725 extended the deadline for filing applications to 31 December 2027. In August 2026 the Chamber of Deputies passed a bill that would extend it to 31 December 2029 and raise the caps, but it is still in the Senate.

Almost every house in Chile has something that is not on the plans: an extension, an enclosed barbecue area, a room that went up when the second child arrived. As long as nobody looks, nothing happens. The problem shows up the day you need to sell, mortgage or inherit, and that is when the lack of final municipal approval stops being an administrative detail.

What final municipal approval is, and why it matters so much

Final municipal approval is the act by which the Municipal Building Department certifies that what was built matches the permit granted and complies with the regulations. It is the document that closes the cycle: first the building permit, then the construction, and finally the approval.

Without it, for legal purposes the building does not exist, even if you have lived in it for twenty years. That has very concrete consequences.

• The bank will not finance it. The valuation counts what has been approved, not what has been built, and the loan falls through or shrinks. We cover this in why the bank can block the sale.
• The price takes a hit. You can still sell, but the buyer discounts for the cost and the risk of regularising it. That is covered in whether you can sell a house without final municipal approval.
• Insurance may not cover what has not been declared or approved.
• You cannot subdivide or set up a condominium regime with buildings that have not been approved.
• You remain exposed to fines from the Municipal Building Department, whose amount and how to defend against them we explain here.

What the ley del mono is, by name and number

The nickname hides a specific law: law 20.898, which sets out a simplified procedure for regularising self built homes. Simplified means the permit and the approval are obtained in a single step, with fewer supporting documents and lower cost than the general route.

It is not an amnesty or a pardon. It is a procedure with requirements, and anyone who does not meet them is left out and has to go through the ordinary route. Nor is it permanent: it was born with a deadline and has been extended by successive laws. The latest, law 21.725, pushed the deadline for filing applications back to 31 December 2027.

The two regimes, which are almost never told apart

This is the source of almost all the confusion out there. The law does not have a single cap: it has two tiers, with different requirements, which is why you see contradictory figures everywhere.

In both cases the building must have been built or extended before 4 February 2016. That date does not move: it is not a matter of being so many years old, it is a specific day, and an extension made after that date does not qualify through this route, however small it is.

The detail that works in your favour and almost nobody knows. The appraisal that counts is not the current one: it is the one on the certificate from the Servicio de Impuestos Internos (the Chilean tax authority) for the first half of 2016. If your property increased in value since then, and most did, you still qualify using the 2016 figure. It is worth requesting that certificate before assuming you are excluded on appraisal grounds.

Who is left out

There are two exclusions that rule you out outright, and it is worth checking them before commissioning any plans.

• Having pending complaints for breach of planning rules before the Municipal Building Department or the Local Police Court. If a neighbour has already reported you and the proceeding is open, this route is not available while it remains active.
• Being located in a risk or protected area. If the land is in a flood zone, a landslide risk zone, or an area protected by the planning instrument, simplified regularisation is not available. How to check this is in how to find out if land is in a flood zone.

The file: what has to be submitted

The application is filed with the Municipal Building Department of the relevant commune, with the ministry's form and the supporting documents that go with it. Here is the list, and it must be signed by an architect or the competent professional, depending on the case.

Of everything on that list, proof of age is what holds up the most applications. It is worth gathering it first, because if you cannot prove the building predates February 2016, the rest of the file is of no use.

The deadline is running, and this time it has a date

31 December 2027 is the current deadline for filing applications. It is the deadline for submitting the application to the Municipal Building Department: the procedure itself can finish afterwards.

The bill that would extend the ley del mono to 2029

In April 2026 a private member's bill to reform law 20.898 was filed, bulletin 18.189-14. The Chamber of Deputies passed it on 19 August 2026 and sent it to the Senate, where the Housing Committee approved it in general on 1 September; the Executive has submitted amendments and it carries an urgency. These are its main changes, according to the text passed by the Chamber:

• New deadline: 31 December 2029.
• New cut-off date: buildings erected before 28 November 2025 could be regularised, instead of 4 February 2016.
• Higher caps: the first regime would rise to 120 square metres and 2,000 UF, and the second to 180 square metres and 3,000 UF.
• Fewer rules blocking regularisation: homes of up to 120 square metres would be exempt from planning rules that prevent regularisation.
• Shorter deadlines for the Building Department: from 90 to 60 working days in the housing procedure.
• Municipal regularisation teams: municipalities could set them up to help, free of charge, the most vulnerable 60% of the Social Household Registry, older adults, people with disabilities and rural residents.

Until the Senate approves it and the law is published, the 2027 deadline, the 2016 cut-off date and the current caps apply. Planning around an extension that does not yet exist is the most common way of being left out.

The practical takeaway is simple. Putting the file together takes time, especially the proof of age and the plans, and the Municipal Building Department can raise observations. Starting the process in the last six months is betting there will not be any.

I built a 36 square metre extension without a permit: what can I do?

It is one of the most common questions, and the answer depends on when it was built and on the size of the whole house, not just the extension.

• Under the current law, the extension qualifies under the ley del mono only if it already existed on 4 February 2016 and the whole home, extension included, fits one of the two regimes: up to 90 square metres and 1,000 UF, or up to 140 square metres and 2,000 UF.
• If the bill passes as it left the Chamber, it would qualify if built before 28 November 2025 and the whole home does not exceed 120 square metres and 2,000 UF, or 180 square metres and 3,000 UF.
• Outside the ley del mono, the General Urban Planning and Construction Law has a permanent simplified regime for extending social or incremental housing, and homes whose construction is valued at no more than 520 UF, with municipal fees halved.
• Through the general route, an extension of up to 100 square metres is minor works, handled with a minor works permit and its approval.

Until the extension is regularised, it is exposed to fines from the local police court of 0.5% to 20% of the construction budget, and the judge can order the works to stop or be demolished. We explain how they are calculated and how to defend yourself in fines for building without a permit.

If you do not qualify, there is still a way forward

Falling outside law 20.898 does not mean you cannot regularise. It means going through the general route: a building permit and final municipal approval, with the full project and payment of the relevant municipal fees. It is longer and more expensive, but it reaches the same result, and the breakdown is in how much it costs to obtain final municipal approval.

There are two situations where the problem comes earlier and has to be resolved first. If the property is not registered properly, regularisation of title comes first. And if what was built sits on rural land, the regularisation has to work alongside the rural construction rules, which are covered in how many houses can be built on a plot.

Frequently asked questions about the ley del mono

Do I need the building permit first?

No, and that is precisely the point of the simplified procedure: the permit and the approval are obtained in one step. Through the general route you would have to get the permit first and then apply for approval, with two separate processes and two payments.

My extension is from 2019. Can I use this route?

Not through this route. The law requires the construction or extension to predate 4 February 2016, and that date admits no exceptions. In that case, what applies is regularisation through the general route.

My house is worth more than 2,000 UF today. Am I excluded?

Not necessarily. The appraisal that counts is the one on the certificate from the Servicio de Impuestos Internos for the first half of 2016, not the current one. Many properties that exceed the cap today still qualify using the figure from that date, so the first step is to request that certificate.

A neighbour reported me. Can I still regularise?

As long as there is a pending complaint for breach of planning rules before the Municipal Building Department or the Local Police Court, this route is not available. The first step is to resolve that proceeding, and there it matters whether the infringement has become time barred.

Does it work for a barbecue area or a storage shed?

The law is designed for homes and their extensions, and it also covers small, harmless businesses and social facilities. An accessory building is assessed on whether it counts towards the home's built area or not, and that calculation is what determines which regime it falls under.

How do I prove the construction predates 2016?

With anything that has a date: photographs, receipts for materials, contracts with the builder, utility bills for the extended property, and above all historical satellite images, which tend to be the cleanest evidence because they show the building existing on a given date.

What happens if I never regularise?

The house stays standing and you carry on living there. What you cannot do is sell it well, mortgage it, insure what has not been declared, or pass it on without carrying the problem over to your heirs. In practice, the cost is not paid in fines: it is paid in the price, on the day you need to sell.

Will the ley del mono be extended to 2029?

That is what the bill passed by the Chamber in August 2026 proposes: a deadline of 31 December 2029, buildings erected before 28 November 2025 and caps of 120 and 180 square metres. It is in the Senate and is not law yet, so today the 2027 deadline and the 2016 cut-off date apply.

How we do it

We start by working out whether the case qualifies, which is a short review that determines everything else: the 2016 appraisal certificate to see which regime applies, the actual measured area, and whether there are pending complaints or the property is in a risk area. That tells us whether to proceed under law 20.898 or through the general route.

Next comes the file: the survey of what was actually built, the scale plans, the specifications and the professional's report. Our own team of surveyors and architects does the survey and the plans, so when the Municipal Building Department raises an observation it is corrected and resubmitted without coordinating between separate offices. If you want a sense of scale before talking to us, the regularisation cost calculator gives a reference figure.

When the problem lies earlier, we resolve it first: a title study if ownership is unclear, regularisation of title if the property is not registered, or the posesión efectiva, the Chilean grant of probate, if it comes from an estate that was never processed. Regularising the construction on a title that is not in order is starting with the roof.

Send us the property's roll number and a photo of what was built, and we will tell you which regime it falls under, what documents you will need, and whether it is worth speeding up the process before the deadline.