What you need to file online
Barcelona City Council's Oficina Virtual asks you to identify yourself and sign electronically to file a comunicat, a works licence or the prior consultation. The works procedure page lists as accepted idCAT Mòbil, idCAT Mòbil+ and Cl@ve, which work with one-time passwords sent to your phone; the electronic DNI; and the idCAT Certificat and other qualified digital certificates, such as the FNMT personal certificate.
Yes, you can get them yourself, including as a foreigner with an NIE. What differs is the route: idCAT Mòbil is the Catalan administration's system and the quickest if you have a TIE and a CatSalut health card; Cl@ve is the national system and also works for the tax agency and social security; and the FNMT certificate is a file you install on your computer that works almost everywhere, but with an NIE it requires going in person to verify your identity.
When you need it and when you don't
You need it if you are going to file the prior consultation, the immediate or deferred notification, or the licence application yourself from home, for example for the renovation of your flat in the Eixample. It also lets you check the status of the file and send documents when asked.
You don't need it in three cases. If you go in person: the works procedure can be done with an appointment at the district's Oficina d'Atenció Ciutadana. If you authorise a representative, such as your architect or an administrative agent (gestor), who files with their own ID; in that case the prior consultation must already be made with those holder and representative details. And for paying: according to the Institut Municipal d'Hisenda, the ICIO can be paid online by card or Bizum without a digital certificate. For a house in Castelldefels or another town, you will use that council's e-office, but idCAT Mòbil and Cl@ve are usually accepted by Catalan administrations; check the procedure page.
What each option asks for
Anyone over 16 with a DNI, NIE, TIE or passport can get idCAT Mòbil. Online there are two routes: with a DNI or TIE plus the individual health card (TSI) from CatSalut or MUFACE, or with video identification by selfie, which an operator reviews within about 48 hours. In person, at an idCAT Mòbil registration office, you bring your ID and your phone and sign an application form.
Cl@ve has a basic and an advanced level. Registration by video identification is, for now, only open to Spanish citizens with a valid DNI. With an NIE you can request an invitation letter online: you are asked for the support number printed on your document, the letter arrives by post and you have 60 days to use its CSV code; that gives you the basic level, which is not valid for every service and does not allow Cl@ve Firma. The advanced level is obtained in person, by appointment, at a registration office; foreigners prove their identity with a passport or travel document.
The FNMT personal certificate is free for adults with a DNI or NIE. With an NIE, the FNMT says identity can currently only be verified in person, not by video. At the verification office you show the request code and your foreigner's card with the NIE plus your passport, or the official NIE document plus your passport.
Step by step for your situation
If you have a TIE and a Catalan health card, go for idCAT Mòbil online. Open the Consorci AOC's idCAT Mòbil registration assistant, enter your ID details, mobile number and email, type in the code sent by SMS and click "Dona'm d'alta". Download the receipt. From then on, on the Oficina Virtual you choose idCAT Mòbil when you start a procedure, enter your document number and get a code on your phone each time you log in or sign.
If you don't have a health card, or you hold an EU citizen certificate instead of a TIE, try the selfie registration in the same assistant or go to a registration office. If you also want Cl@ve for the tax agency, request the invitation letter and finish registering with the CSV when it arrives.
For the FNMT certificate, order matters. First you install the configuration software shown on the FNMT e-office; then you submit the request online and get a code by email; then you book an appointment and go to a verification office, for example at the tax agency or social security, with that code and your documents; and roughly an hour after verification you download the certificate using the same code. Make a backup straight away.
Afterwards: using it for works procedures
With any of these systems you log in to the Oficina Virtual, open the prior consultation or the works procedure and click Iniciar el tràmit. The system identifies you, you fill in the form, attach the PDFs and sign at the end. Always keep the registry receipt it generates: it proves your filing date, and for a comunicat diferit the one-month period runs from there.
Think about who will sign the whole file. In Barcelona, the person filing the works procedure must be the same person who made the prior consultation, because the consultation number is tied to their ID document. If your partner made the consultation with their idCAT, your partner must also file the comunicat, or the consultation has to be amended. And if your Cl@ve is basic level and at some step you are asked to sign and it won't let you, use idCAT Mòbil or the certificate, or upgrade Cl@ve to the advanced level.
Common mistakes
Trying FNMT or Cl@ve video identification with an NIE: it is not available for NIE holders today and you lose an afternoon. Requesting the Cl@ve invitation letter and letting the 60 days pass. Requesting the FNMT certificate on one computer and trying to download it on another, or wiping the computer without a backup. Registering idCAT Mòbil with a phone number you later change without updating your details. And, above all, preparing everything in one person's name and filing with someone else's ID.
If you live outside Spain for much of the year, consider authorising your technician as representative from the prior consultation onwards, rather than depending on an SMS to a number you may not have at hand. The requirements of these systems change often, so check each one's current page before you start. If you would rather not deal with it, BCN YARD files the works documents for you as your representative.