Coal mining contribution bases 2026: how much companies pay and what they must do

Key data

Coal mining companies face an immediate obligation: recalculate and regularize their Social Security contributions from January 2026. The Order ISM/727/2026, published on July 15 in the BOE, sets the standardized contribution bases for common contingencies for the Special Regime for Coal Mining with full retroactivity to the start of the fiscal year.

The absence of new General State Budgets has led to the extension of those from 2023, adapted through Royal Decree-Law 3/2026. The bases have been calculated taking as reference the contributions for work accidents and occupational diseases for fiscal year 2025.

What does this regulation establish?

Order ISM/727/2026 publishes the standardized contribution bases for common contingencies applicable throughout fiscal year 2026 in the Special Regime of Social Security for Coal Mining. These bases determine the amount on which the quota that both company and worker must pay to Social Security is calculated.

The bases are structured in detailed tables that vary depending on three key variables:

• Professional category: each job position has a specific daily base assigned.
• Specialty: within each category there may be differences due to specialization.
• Mining zone: the regulation distinguishes between two geographic areas with differentiated bases.

The calculation method is based on contributions for work accidents and occupational diseases recorded in 2025, which serve as a reference for standardizing the common contingency bases for 2026. Since new General State Budgets have not been approved, the extension of those from 2023 is applied with the adaptations introduced by RDL 3/2026.

Economic and operational impact

The main impact is not just the amount of the new bases, but the retroactivity: the order is effective from January 1, 2026, but is published in July. This means that companies have been contributing for months with provisional or previous reference bases, and now must calculate and pay the accumulated differences.

To dimension the impact, consider that the difference between the minimum base (€61.72/day) and the maximum (€167.71/day) is €105.99/day per worker. In a month of 30 days, this represents a range of between €1,851.60 and €5,031.30 of monthly base per employee, to which the applicable contribution rates are applied.

Companies with higher category staff or in areas with higher bases will accumulate more significant contribution differences for the months already elapsed in 2026. The specific deadline for regularizing these differences will be set by the State Secretariat for Social Security through specific communication.

From an operational perspective, HR and administration departments must:

• Recalculate the contributions of each worker from January 2026 with the new bases.
• Quantify the differences month by month for each category and zone.
• Prepare regularization documents to submit them within the established deadline.

Who does it affect?

• Coal mining companies classified in the Special Regime of Social Security for Coal Mining, both in the First Zone (Asturias) and in the Second Zone (Northwest).
• Workers of such companies, whose contribution bases are set according to their professional category and specialty.
• Management firms and labor advisors who manage payroll and social security for companies in the sector.
• HR and administration departments responsible for settling Social Security contributions.

Practical example

Suppose a mining company in the First Zone (Asturias) with a worker in a category that has been assigned a daily base of €120/day (within the range of €61.72 to €167.71). In a month of 30 days, the monthly contribution base for common contingencies would be €3,600.

If during the months of January to June 2026 (6 months) the company had been applying a lower provisional base, for example €110/day, the accumulated difference would be:

• Daily difference: €10/day
• Monthly difference: €300 of base
• Accumulated difference in 6 months: €1,800 of base per worker

The applicable contribution rates would be applied to that base difference to calculate the additional quota to be paid in the regularization. In workforces with several dozen workers in high categories, the total amount of regularization can be significant and should be planned in advance.

What should companies do now?

1. Locate the applicable bases table: identify the professional category, specialty and mining zone (First Zone-Asturias or Second Zone-Northwest) of each worker to apply the correct daily base according to Order ISM/727/2026.
2. Recalculate contributions from January 2026: compare the bases applied in the months already settled with the new standardized bases and quantify the accumulated differences per worker.
3. Prepare regularization documentation: calculate the total amount of contribution differences to have it ready before the State Secretariat for Social Security sets the special regularization period.
4. Update payroll systems: enter the new bases in payroll management software so that contributions for the remaining months of 2026 are calculated correctly from now on.
5. Monitor State Secretariat communication: the specific deadline for paying contribution differences will be expressly set by the State Secretariat for Social Security; not acting before knowing it can generate errors, but it is also not advisable to wait to have the calculations ready.

Official source

Consult complete regulation in official source

Notice: This article is for informational purposes only and does not constitute legal advice. For specific decisions, consult a qualified professional. Source: https://www.boe.es/diario_boe/txt.php?id=BOE-A-2026-15379