Time records and substantial modification: KAEFER case (Avilés, 2026)

Legal notice: This article is informational and does not constitute legal advice. It summarises judgment STIS 756/2026 (Avilés First-Instance Court, Social section, seat 2), ruling 104/2026 of 27 March, ECLI:ES:TIS:2026:756. It is a first-instance ruling and not final: an appeal (recurso de suplicación) may be lodged before the TSJ of Asturias.

The case

A worker in the industrial insulation sector, with continuous service since 2002 and transferred to KAEFER Servicios Industriales SAU in 2019, was providing services at FERTIBERIA’s facilities in Corvera de Asturias. Agreed working time: 40 hours per week, 1,728 hours per year under collective agreement, schedule 07:15 to 15:15 (8 hours per day).

On 20 February 2026, KAEFER sent him a written communication reminding him that, according to clock-in records, the data did not match the established schedule and that he had to strictly comply with 07:15–15:15. The worker responded with a claim for substantial modification of working conditions (Art. 41 ET — Workers’ Statute), alleging that the company was effectively adding half an hour to his daily shift through de facto means and that the communication was also a reprisal (breach of anti-retaliation protections). He sought to return to the previous schedule plus €7,501 in damages.

The reprisal argument does not come out of nowhere. The ruling cites three prior judicial precedents involving the same setting: a final judgment 473/2024 from the Avilés Court itself, which had already ruled in the claimant’s favour against KAEFER over the removal of the “travel” and “mileage” supplements; another judgment 468/2024 in favour of a co-worker (Pablo) on the same issue; and a third one from 2025 (373/2025), initially dismissed on jurisdictional grounds, overturned by the Asturias High Court (TSJ) and currently under cassation appeal (recurso de casación) brought by the company. It is against that prior backdrop that the 20 February communication arrives.

What the company’s clock-in records show

The core of the case is the very clock-in records KAEFER produced:

Period	Clock-in	Clock-out	Average shift
2023	~07:45 (15 min before 08:00)	~15:30	—
2024 to Sep 2025	07:15–07:20	~15:00	7.77 h
15 Sep 2025 – 23 Feb 2026	07:27–07:32	~15:00	7.52 h
24 Feb – 17 Mar 2026 (after notice)	07:10–07:15	exactly 15:15	8.05 h

What that data shows is the opposite of what the claim argued. The shift the company was no longer willing to tolerate was a systematically under-worked shift (7.52 h average in the most recent stretch). After the 20 February communication, the worker began clocking in averaging 8.05 h without the company changing anything else.

How KAEFER’s clock-in procedure is set up

KAEFER has a formal procedure for managing and recording working time, with several relevant elements that the ruling accepts as proven facts:

• General obligation: every worker with the means to clock in must do so following the established rules.
• Dual system: QR code (via tablet, corporate mobile or computer) and the employee portal.
• Time framework: the shift begins already dressed in work clothes and PPE, “en el horario de la obra, no el que estipule el trabajador” (on the project schedule, not the one the worker decides). Tolerated margin: 10–15 minutes.
• Lunch break: if the shift is interrupted, workers must clock out and back in.
• Communication and discipline: the procedure is posted on notice boards, has been communicated in writing to all workers, and the company has warned it will sanction failure to clock in and irregular practices.

It is a system that, far from being dead paper, is designed as an operational source of evidence against non-compliance.

What the judge rules

The First-Instance Court dismisses the claim in full. The reasoning rests on two pillars:

1. There is no substantial modification, but rather exercise of the employer’s ius variandi. Reminding the worker of his contractual schedule does not alter conditions; it restores them. A substantial modification (Art. 41 ET) requires a change “que altere y transforme los aspectos fundamentales de la relación laboral” (that alters and transforms the fundamental aspects of the employment relationship), and here what changes is the worker’s conduct, not the agreed condition.
2. The burden of proof lies with the claimant (Art. 217.2 LEC — Civil Procedure Act). The worker alleged he clocked in from 07:30 to 15:00; the records produced by the company showed habitual entry at 07:15–07:20 since 2024. That documentary evidence “atestigua de forma fehaciente el devenir contractual” (reliably attests to how the contract actually unfolded) and dismantles the claim’s premise.

The judge also leaves a relevant practical observation: the company had room, knew it, and yet one of the shifts in March itself falls below 8 h without consequences. What KAEFER closes is the flexibility tap it had itself tolerated for years.

Why this ruling matters

It is a first-instance ruling and does not set doctrine. But it illustrates a scenario that the digital time-records regime is making increasingly common:

Clock-in records also play in the employer’s favour when the burden of proving the worker’s non-compliance falls on the employer. They help the Labour Inspectorate and the worker to evidence excessive working time, but they equally help the employer to support corrective or disciplinary measures against those who do not meet the agreed schedule — and to do so without those measures being reframed as a substantial modification. The logic is the same as the one we covered in another recent case where digital time-tracking shielded a company against an overtime claim.

There is another lesson, less rhetorical and more operational: those who keep good records gain room to manoeuvre. KAEFER was able to build its defence on three tables and an email precisely because it had clean data from 2023 to 2026. Had the records been a manipulable Excel sheet or paper timesheets, the evidentiary outcome leans the other way, in line with the criteria of the CJEU in CCOO/Deutsche Bank (C-55/18) and the doctrine applied by the Supreme Court.

A tactical detail that KAEFER’s procedure makes explicit and that the ruling accepts without qualification: the 10–15 minute margin published in its internal rules. That reasonable band neutralises allegations of excessive rigidity without giving up the objective duty to work 8 hours.

One front remains outside what the ruling decides: the worker’s complaint over breach of anti-retaliation protections (reprisal for prior judicial claims) can still be appealed in suplicación to the TSJ of Asturias under the LRJS (Labour Procedure Act). The debate may continue, but the company arrives with an evidentiary record that is hard to challenge on that terrain.

What to demand, as an employer, from a time-records system to defend yourself in a case like this

The ruling does not put it in these terms, but everything KAEFER does right fits what Art. 34.9 ET and the general digital time-records regime already require or will require:

• Historical traceability: being able to show a worker’s clock-in pattern over years, not just the disputed month.
• Immutability: the company cannot tamper with the record after the fact (and neither can the worker). Here, the evidence is signed by the system itself, not produced by one of the parties.
• Published and communicated procedure: a clock-in policy that is known, accessible on notice boards and by email, with clear rules on QR/portal, clothing, PPE, breaks and tolerated margins.

To those three material elements is added a procedural one that mattered here: the 20 February communication operates as a prior warning, not as a sanction. The judge reads it as a reasonable exercise of managerial power, not as a reprisal. Without that sequence (clean data → documented warning → margin to correct → evidence of effective correction), the same factual scenario tilts the other way.

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Source: STIS 756/2026, Avilés First-Instance Court (Social section, seat 2), ruling 104/2026 of 27 March, ECLI:ES:TIS:2026:756, available on CENDOJ. Non-final ruling (appeal in suplicación may be lodged before the TSJ of Asturias on the grounds of fundamental rights protection).