Invoice for water connection despite payment through property price?

One must also pay attention to the wording in the notarial deed. That the seller, for example, "provides" does not mean that she also bears the costs. We had very significant ambiguities in the first draft regarding development services.

OT: I keep wondering throughout this thread who came up with the idea to base the water connection costs of a property on the floor area? Do the connections for the 80m² mini bungalow look different in any way from those for the 300m² city villa?

Once again as a supplement to my last post. You owe the production costs to the municipal utilities, who of course hire a civil engineer to make the connections. There must be a concrete and transparent breakdown of the total amount. Ask the municipal utilities.

OT:
I have been wondering throughout this thread who came up with the idea to base the water connection costs of a property on the floor area? Do the connections for the 80m² mini bungalow look any different in any way than those for the 300m² city villa?

The fact that it must be measured accordingly follows from Article 5 Paragraph 2 Sentence 2 No. 1 KAG in conjunction with §16 of the Building Use Ordinance.

As with many laws, the sensibility can be debated.

However, it is about compensating an advantage gained through development.
Someone with a higher floor space ratio now has the possibility to use the advantage on a larger area than someone with a smaller floor space ratio.
The advantage relates to the objective point of view. Someone with a corner plot who can only access their property from one side may not see that they have an advantage through the second street. Objectively, however, they do have this advantage because they would be able to develop their property from two sides.
Therefore, they must pay development contributions for both sides. Sounds unfair or strange, but it is so.
So, for example, a greater advantage is assumed with a larger floor space ratio, similar to how in the calculation of road construction costs the plot size is used, although in most cases only one access road to the property is built.
Thus, the sewer must sometimes be dimensioned larger because someone with a larger floor space would be capable of producing more wastewater than someone with a smaller floor space. Here, one simply has to take the natural point of view, according to which it seems usual that with a larger floor area, for example, several bathrooms or several water consumers are installed.
Perhaps it helps to note that contributions are due for the possibility of use, fees only for actual use.

So you apparently have to pay additional construction contributions because, as you already wrote yourself, you only made a flat-rate prepayment.

That is clear to me - there is also a notice coming from the municipality. In addition to that, we have received an invoice.

You also have to pay attention to the wording in the notary contract. For example, just because the seller "constructs" does not mean she also bears the costs. We had very large ambiguities in the first draft regarding development services.

Interesting. What was changed in your case then?

Maybe the hint helps that contributions become due for the possibility of use, fees only for actual use.

Overall, I find the calculation very adventurous

Was summoned to the municipality today. Interesting how much they interfere, although until now it’s only about an invoice from company A to consumer B. Intimidation setup, mayor, four employees, one from the company. Key statement of the conversation: "We have always done it this way." Question: "Okay, and where does it say that?" – then they can’t show it... Clearly noticeable fear that if one does not pay, no one pays. Trick questions like "Do you understand the content of the invoice, is that correct?" so that under witnesses it is confirmed that the invoice is "in order"...

Very subtle...

What did they say the invoice is for and what items does it consist of?

I can also write you an invoice if you want?

Maybe they miscalculated somewhere in your favor and want to charge it afterward?