Luxembourg does not have a separate tax number that you apply for as a stand-alone chore. What you need is one identifier, the matricule, that follows you across the tax office, social security, your employer and your bank. Getting your Luxembourg matricule number is mostly a by-product of registering at your commune.
What is the Luxembourg matricule number?
It is the numéro d'identification national, 13 digits long (the format is set out in the EU Official Journal's note on tax identification numbers). It is attributed when you are entered in the Registre national des personnes physiques (RNPP). For a resident, that happens through your declaration at the commune: the data you give there feeds the register, which then gives you the number. Guichet.lu does not charge for it.
How do you get your matricule when you live in Luxembourg?
- Declare your arrival and register at your commune. The steps are in our guide to residence in Luxembourg for EU citizens.
- Start work or register as self-employed. An employer declares you to the CCSS (the social security centre) within eight days. A social security card follows automatically.
- Wait for the tax card. The tax administration (ACD) issues your fiche de retenue d'impôt automatically after affiliation, in about 30 working days on average.
If the number does not reach you, ask your commune. Do not expect a reply by email: the register does not send the number electronically, for privacy reasons.
Which documents and costs are involved?
For the resident route, you need the documents of your registration at the commune. For a non-resident who needs the number for a professional reason, Guichet.lu asks for an ID document signed electronically, a residence certificate under six months old and proof of the professional reason. The request is made online on MyGuichet.lu without authentication, it costs nothing, and an extract is sent by post within two weeks of the data being updated.
If you are unsure whether you need the resident route or the professional-reason route (a company director living across the border, say, or a freelancer), Moovy can compare the official criteria with your situation and list the documents to bring. It prepares your file; the register and the commune issue the number.
What problems do people run into?
- Starting work with no tax card. Without it your employer applies class 1 with a minimum 33% withholding. If nothing arrives within 30 working days, chase the RTS office.
- Moving house without telling the commune. Your tax card is updated from that change, so a missed update can distort your withholding.
- Asking for a number for a company. The number belongs to a person, not a business.
- Expecting an answer by email. It will not come that way.
Does it differ by nationality?
EU, EEA and Swiss citizens follow the same route. British nationals follow the same logic once they hold a residence right, either as beneficiaries of the Withdrawal Agreement or as third-country nationals. Check moving to Luxembourg from the UK for the permit side.
How does the matricule connect to everything else?
It is how you will be recognised on MyGuichet.lu, how the CNS identifies you for reimbursements (see healthcare in Luxembourg for expats) and how the tax office matches your return. If you are a cross-border worker, you still need one for your Luxembourg job. Keep it safe, but do not be afraid to quote it: it is the thing every Luxembourg office asks for first.
What happens between registering and receiving the tax card?
It helps to picture the chain as a relay, because each runner hands a baton to the next.
- The commune records your arrival and registration.
- The national register gives you your number.
- Your employer declares you to the CCSS, quoting the number.
- The CCSS affiliates you and sends the social security card.
- The tax administration sees the affiliation and sends the tax card, to you and electronically to your employer.
If one runner stops, the others wait, so the sensible move is to complete step one first and ask the commune for your number if it has not reached you. The Guichet.lu page on tax cards says that a new card is also issued after certain changes, such as a new employer or a change of address or civil status.
What if you are self-employed or a company director?
A self-employed person registers with the CCSS personally, using the self-employed entry form, and then waits for the same card. Someone who has to run a Luxembourg business while living abroad may need the number before any commune registration. That is the professional-purpose route described above: free, done online, and answered by post. Guichet.lu stresses that the number is attributed to a natural person, never to a company, so a director asks for their own.
What should you do if the number is wrong or missing?
Contact your commune first, since it holds your registration. Check that your name, date of birth and place of birth were entered exactly as on your passport. A typo copied into the register can follow you into your tax and social security files. If you spot an error on your tax card, report it to the RTS office and tell your employer, who works from the electronic version.
Also remember that the number you receive here is not a substitute for the tax identification number of your previous country. If you still owe tax in your old country in the year you left, you will quote that number on its own forms; the convention between Luxembourg and your former country decides who taxes what. Ask the tax administration (ACD) how the convention applies to your year of arrival, and see the guide to moving to Luxembourg for the other first-weeks steps in order.
Where will you be asked for your Luxembourg matricule number?
Almost everywhere that matters, and usually in the first fortnight.
- Your employer needs it to declare you to the CCSS, which is what triggers your social security card and, in turn, your tax card.
- The health fund (CNS) uses it when you ask for reimbursements, and when you add a spouse, partner or child as co-insured persons.
- The tax office matches your returns and your annual adjustment to it.
- MyGuichet.lu links your account to it when you log in with LuxTrust or GouvID. If you come from a country whose electronic identity is recognised, Guichet.lu says you can even request a number online through the eIDAS registration procedure.
- Your bank may ask for it when it checks your tax residence, although the official pages we read do not make it a condition of opening an account.
If you are comparing countries, note that Luxembourg's number is not issued for a single purpose. The same 13 digits serve social security, taxes and the register of residents. That is convenient once you have it and awkward until you do, because there is no separate form to fill for it: the number follows from registration.
How can you check that your Luxembourg matricule number is correct?
Look at your social security card and your tax card. Both should show the same 13 digits, your name and date of birth as in your passport, and your current address. If one differs, the cause is almost always a mismatch at registration, and the commune is the place to start. Ask for a corrected record, then ask your employer to resend the declaration if it was filed with an error.
A final tip: store the number in a safe place on your phone or in a password manager, not in an email. The register itself refuses to send it electronically, and for good reason.