Correctly calculated under fees law: High fees for sludge from small treatment plants

Instructive fees law decision by the Higher Regional Court Baden-Württemberg (VGH Baden-Württemberg) on the calculation of fees for sludge from small treatment plants

Municipal user fees: Basic principles of tax law

Municipal user fees are a central instrument for financing public facilities. Their legal limits do not arise from a desire for uniformity, but from the fees law guiding principles of municipal tax law. Decisive are in particular the cost coverage principle, the equivalence principle as well as the allgemeine Gleichheitssatz des Art. 3 Abs. 1 GG.

The cost coverage principle requires that fees calculated in accordance with business administration standards do not exceed the eligible costs of the respective public facility must not exceed, but also need not necessarily reflect them exactly. The municipal by-law maker has a broad scope for forecast and discretion in this regard, in particular when determining future costs and utilisation of services.

The equivalence principle does not require a mathematical balance between the fee and individual use, but merely a comprehensible, objectively justified relationship between the amount of the fee and the value of the public service. The equality principle does not prohibit differentiations, but only those that lack an objective reason. Typifications and flat-rate calculations are permissible if they are practical and realistic.

These general principles of fees law apply on a facility-specific basis. What is therefore always decisive is which public facility is specifically utilised – not whether it is abstractly the same municipal task.

Wastewater disposal as a fees law differentiated task

Municipal wastewater disposal is not a uniform process, but can be divided into different public facilities on a legal and organisational basis. Municipalities may operate the centralised wastewater disposal via the sewer network and municipal treatment plants on the one hand and the decentralised wastewater disposal via small treatment plants and sealed tanks on the other hand as independent facilities.

This differentiation is of considerable importance under fees law. Whereas in centralised wastewater disposal typically large quantities of wastewater with relatively homogeneous pollution load are generated, decentralised wastewater disposal is characterised by small quantities, but significantly higher contamination of the resulting sludge. In addition, there are specific additional costs, such as for removal, transport and acceptance of the sludge.

Under fees law, this necessarily leads to the following: Centralised wastewater fees and fees for small treatment plants must not be mixed with one another or compared schematically. Each facility is to be calculated independently. Costs that are clearly attributable to a facility may only burden its users. Costs of jointly utilised facilities – in particular treatment plants – must be distributed in accordance with the causation principle.

The specific case in dispute: Fees for sludge from a small treatment plant

Against this background, the Administrative Court of Appeal Baden-Württemberg (Verwaltungsgerichtshof Baden-Württemberg) had to decide on the lawfulness of fees notices for the removal and disposal of sludge from a small treatment plant. The claimant was the owner of a plot of land with no connection to the central sewer system. His wastewater was treated via an approved small treatment plant; the resulting sludge was removed by the municipality and disposed of at a municipal treatment plant.

The municipality had structured the central and the decentralised waste water disposal by way of two independent public facilities. For the decentralised disposal, it fixed fees that were significantly higher than the fees for central waste water disposal.

The claimant challenged several fee notices. He argued that the fees violated the equivalence principle and the equality principle, as they amounted to a multiple of the central waste water fees. Furthermore, he objected to the inclusion of transport costs and the inclusion of the costs of a faecal acceptance point. The Administrative Court Stuttgart followed this reasoning and declared the fee calculation to be defective.

The legal considerations of the Higher Regional Court: Separation of facilities and permissible typification

The Higher Regional Court (VGH) Baden-Württemberg set aside the judgment of the lower court and confirmed the lawfulness of the fee notices.

The Senate makes it clear that the municipality was right to treat central and decentralised waste water disposal as independent facilities. It already follows from this that a direct comparison of the respective fee rates is legally flawed. Different facilities may – and must – have different fees if their cost structures differ from one another.

With regard to the jointly used treatment plant, the VGH approves the allocation of costs according to the waste water quantities taking into account the degree of pollution. The Senate expressly confirms that the cleaning effort for sludge from small treatment plants is typically a multiple of the effort for normal domestic waste water. The use of a typifying pollution factor of 25 is professionally recognised, practicable and legally unobjectionable.

What is decisive is that this factor does not necessitate a specific fee ratio, but merely serves the causal allocation of costs. Additional costs that are attributable exclusively to decentralised waste water disposal – in particular removal and transport costs as well as costs of a faecal acceptance point – may be fully included in the fee calculation.

In the Senate's view, there is no breach of Art. 3 Abs. 1 GG nor a breach of the equivalence principle. Differences to other municipalities are irrelevant under fee law. The additional private costs that operators of small treatment plants must bear for maintenance and operation are also legally irrelevant for the municipal fee calculation.

Recommendation for practice: Do not compare fees, but calculate them

The judgment of the VGH Baden-Württemberg vom 18.12.2025 – 2 S 796/25 makes clear that municipal fees must not be compared abstractly, but examined on a facility-specific basis. Particularly in the area of waste water disposal, the differentiation between central systems and small treatment plants is legally mandatory and regularly leads to significantly different fees.

Our practical tip: Both municipalities and fee payers should have fee notices and by-laws examined not based on feeling, but on the basis of the calculation. Our law firm, specialised inter alia in municipal law and administrative law, AVANTCORE Rechtsanwälte in Stuttgart can clarify early on whether fees are being lawfully charged – or whether taking action against erroneous calculations is worthwhile.