How to check a window company before you pay

A well-written quote does not prove that the company exists, that it is up to date with its obligations, or that anyone will come back if the window fails. Before you pay a deposit, it is worth confirming who is on the other side, as with any large expense.

This guide is only about the company: how to check it, which red flags to look for and what to do if something goes wrong. For the questions to ask during the visit, see the questions for the installer.

5 things to check, a few minutes each

1. Identity: the company name, tax number (NIF) and address on the quote are the ones that will appear on the invoice, and there is a contact that is not just a mobile number.
2. Existence: ask for the access code of the company’s permanent certificate (certidão permanente) from the commercial registry and look it up.
3. Debts: ask for the tax authority’s “no debt” certificate and the Social Security declaration.
4. Licence and insurance: ask whether the company holds an IMPIC licence and ask for proof of workplace accident insurance.
5. Afterwards: a written guarantee, the complaints book and what other customers say.

Step by step

1. Does the company exist?

The permanent certificate is the company’s record in the commercial registry. The company has an access code, and whoever receives it can read the certificate online, on the Conservatória website, with that code alone. According to gov.pt, it shows the company’s registrations and its current articles of association. Ask for the code by email.

Compare the name and address with the quote. If you are dealing with a self-employed person rather than a company, ask instead for the declaration of start of activity and the NIF.

2. Is it up to date with the tax office and Social Security?

The company requests these documents itself, with its own login, and then sends them to you:

• Debt and non-debt certificate (certidão de dívida e não dívida), from the Portal das Finanças. It is issued as a PDF and is valid for 3 months.
• Declaration of contributory situation (declaração de situação contributiva), from Segurança Social Direta.

A refusal proves nothing, but it is an answer. If there is a debt, look at the amount and ask.

3. Does it hold a licence to do works?

According to gov.pt, companies and self-employed workers who carry out private works must apply to IMPIC (the institute that regulates construction) for a private-works contractor’s certificate. The alvará is another title, with limits by value class. On IMPIC’s page, the certificate covers works up to 40,000 euros, excluding VAT.

We have not confirmed whether replacing windows counts as works for this purpose: it depends on the job and its value. Ask the company whether it holds an IMPIC title and what the number is, and write to IMPIC if in doubt. The public lookup we found covers only the public-works alvará.

4. Insurance

To issue the certificate or the private-works alvará, IMPIC requires a declaration from the insurer that workplace accident insurance exists. So ask for proof of that insurance and ask who will be working in your home.

Also ask whether there is civil liability insurance for damage to the property (a broken pane, a damaged wall). We found no official source on what the law requires for small jobs: ask for the insurer’s paper and see what it covers.

5. What other customers say

Search the company name on Portal da Queixa. Consumers post complaints and companies reply. Read the replies and whether the problem was resolved. The formal channel is the complaints book.

Also ask to visit a finished job or to speak to a customer in your area. DECO PROteste says reluctance to give references is a warning sign.

6. The product papers

The company should be able to give you the declaration of performance, the paper that goes with CE marking. Under Regulation (EU) No 305/2011, the manufacturer draws it up for products covered by a harmonised European standard (for windows, EN 14351-1) and must supply a copy when the recipient asks. For the CLASSE+ label and ADENE’s installers, see the CLASSE+ label.

Red flags

Sign	Why it worries	What to do
A very large deposit or full payment up front	You have no leverage if the job stalls	See the section below
A fixed price with nobody measuring	The window may not fit; see how to measure	Ask for a site visit
Pressure: “today only”	It takes away time to compare	Ask for the quote in writing and reply later
Nothing in writing	No proof of what was agreed	Ask for a signed quote
Only a mobile number, no address	Harder to find later	Ask for an address and NIF
No mention of a guarantee	There may be none	Ask for it in writing
“No invoice, cheaper”	You lose the proof of purchase	Say no

No single sign proves the company is bad. Several together are a reason to stop.

Why the invoice matters

The invoice is proof that you bought. According to gov.pt, to claim the legal guarantee the consumer must present proof of purchase, such as the invoice or receipt. Without it, any claim is weaker. DECO PROteste also advises that the quote should itemise the VAT. If you plan to apply for a grant, see window grants and keep the invoices.

How much to pay up front

We found no official rule. DECO PROteste says it is usual to pay 50% to confirm the order, and that asking for more, or everything before the work, is a warning sign. This is guidance, not law. Ask what each payment is for and have it written into the contract, with a date or a stage.

What to put in the contract

• The company’s name, NIF and address, and yours.
• For each window: size, profile (brand and model), glass, opening type and colour.
• What is included: removing the old windows, taking away the rubble and the finishing.
• The price including VAT and each payment, with a date or stage.
• Delivery and installation dates, and what happens if there is a delay.
• Who installs: the company or a subcontractor.
• The guarantee on the product and on the installation, with periods and how to claim. See warranties and certificates.

The legal guarantee: what the law says

Decree-Law 84/2021 applies to consumer purchases of goods. It says the seller is liable for faults that appear within three years of delivery (art. 12) and that in the first two years the fault is presumed to have existed at delivery (art. 13). If installation is included in the sale, the item counts as delivered when the installation is finished (art. 11(2)), and incorrect installation done by the seller, or under its responsibility, counts as a fault (art. 9).

We are not lawyers, and we have not checked how the law applies if your contract is described as works rather than a purchase of windows. In that case, ask DECO or the Directorate-General for Consumers (DGC) for advice.

If something goes wrong

1. Write to the company, by registered letter or by email with a read receipt, describe the problem and ask for a reply by a given date. This is the first step gov.pt gives.
2. Electronic complaints book (livroreclamacoes.pt). The company has 15 working days to reply, according to Decree-Law 74/2017. It records the complaint but does not resolve the dispute by itself.
3. Consumer mediation and arbitration. There are 12 authorised centres. According to gov.pt, the process is free or low-cost and the dispute is resolved within 90 days of the complete file. According to gov.pt, above 5,000 euros the company is not obliged to take part.

Keep the quote, contract, invoice, messages and photos.

Sources

• gov.pt: Guarantee on products bought in Portugal and Decree-Law 84/2021, in the Diário da República: three years, proof of purchase, articles 9, 11, 12 and 13 (Portuguese).
• gov.pt: Resolving consumer disputes, Decree-Law 74/2017, in the Diário da República (complaints book, 15 working days) and Portal da Queixa: how a complaint works: steps, arbitration centres, 90 days, 5,000 euros, public complaints (Portuguese).
• DECO PROteste: Window installation, 7 precautions: 50% deposit, references, VAT (Portuguese).
• Tax Authority: Debt and non-debt certificate and gov.pt: Empresa Online, commercial registry: the tax certificate and the permanent certificate access code (Portuguese).
• IMPIC: Access to the construction activity, gov.pt: Private-works contractor’s certificate and EUR-Lex: Regulation (EU) No 305/2011: licences and workplace accident insurance; declaration of performance (articles 4 and 7).

What to do next

• Run the quote through the quote checker and read the checklist before hiring.
• Use the calculator for a ballpark and the glossary for the terms.
• Replacing old windows? See Replacing old windows.
• Want to hear from someone who does not sell windows? See independent help.