Posting workers to Spain: the Ley 45/1999 declaration and the inspection
Ley 45/1999 requires a posting declaration to the regional labour authority before work starts, except under eight days, and the Inspection checks the A1.
A company established outside Spain that sends staff to carry out a contract on Spanish territory must file a posting declaration with the Spanish labour authority before the service begins, under Ley 45/1999 of 29 November (BOE-A-1999-23164). Only postings shorter than eight days fall outside the requirement.
What Ley 45/1999 requires, and what Real Decreto ley 9/2017 added
Ley 45/1999 governs the posting of workers in the framework of a transnational provision of services. The logic is straightforward. The employment relationship stays with the country of origin, but the work is performed in Spain, and for as long as it lasts the Spanish minimum conditions apply: the pay set by the sectoral and territorial collective agreement covering the workplace, maximum working time, rest periods, holidays, and occupational risk prevention. A firm that pays its home country rate to a fitter posted to a Spanish plant is in breach, even where the contract is perfectly valid at origin.
Real Decreto ley 9/2017 transposed Enforcement Directive 2014/67/EU and tightened the verifiable half of the rule. Since then the posting company must appoint a representative in Spain able to deal with the labour authority and with the Inspección de Trabajo y Seguridad Social, and must keep the posting file available to that Inspection: contracts, payslips, proof of payment, working time records, and each person's A1 certificate. Inspectors can require translations, and a company cannot argue that the paperwork sits at head office abroad.
The declaration goes to the labour authority of the autonomous community where the service will be performed, electronically, before the start date. Each autonomous community runs its own register and its own form, so a posting to Catalonia and a posting to Andalusia are two separate filings even for the same company. If the posting runs longer than declared or the workplace changes, a supplementary declaration is due.
The A1 certificate, and the mistake that costs a full set of contributions
A posted worker keeps home country social security through the A1 certificate inside the EU and the EEA, or through the bilateral social security convention Spain has signed with a third country. The A1 is issued by the institution of the sending state, not by Spain, and it has to exist before the posting starts. Without it, the Tesorería General de la Seguridad Social treats the activity as performed in Spain and demands Spanish registration and contributions from day one, with surcharges. This is the most expensive failure we see on construction and industrial assembly work: the company files the posting declaration on time, then applies for the A1 after the crew is already on site, and a routine inspection visit finds the gap.
The second common confusion is of a different kind. The Ley 45/1999 regime does not replace a work authorisation where the posted person is a third country national without legal residence in a member state. A Serbian company wanting to post Nepalese welders to Spain needs, on top of the declaration, to settle the immigration status of those workers. If the worker already lives and works legally in the sending state, the cross border service is possible. If not, the declaration on its own authorises nothing.
| Item | Who requires it | Timing | Consequence of skipping it |
|---|---|---|---|
| Posting declaration | Regional labour authority | Before the start, except under eight days | Labour infringement, Inspection penalty |
| A1 certificate | Social security institution at origin | Before the start | Spanish registration and contributions with surcharge |
| Representative in Spain | Ley 45/1999 after RD ley 9/2017 | For the whole posting | Inspection cannot obtain the file and penalises |
| Spanish collective agreement terms | Sectoral agreement of the workplace | From day one | Pay differentials and joint liability |
| Work authorisation | Oficina de Extranjería | Before travel, for third country nationals without prior residence | Irregular work, immigration penalty regime |
What the Inspection looks at on a site visit
The Inspección de Trabajo y Seguridad Social works through four questions when it enters a site with posted staff. First, whether a prior declaration exists and matches the people present. Second, whether each of them holds a valid A1 with dates covering the real period. Third, whether pay reaches the Spanish collective agreement minimum, comparing the payslip against the working time record. Fourth, whether the posting is genuine or conceals an unlawful supply of labour, for which the inspector looks at who gives instructions, who provides the equipment, and whether the sending company carries on real activity in its own country.
The Spanish user company is not a bystander. It is jointly liable for wage and social security obligations in the cases the law sets out, which is why the practical step is to ask for a copy of the declaration and of every A1 before the crew is allowed onto the installation. A folder built at the start of the contract prevents an argument with an inspector months later.
Real corridor timings and the order in which filings resolve are set out in the country by country permit timeline, and the fees for the ordinary Spanish hiring route in the cost of hiring a foreign worker in Spain. Where the origin country has a migration agreement with Spain, start with Spain's migration flow agreements.
A posting that holds together is prepared in the reverse of the usual order: the A1 and the immigration status first, the regional declaration next, and flights only after that.
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