Canal construction contribution

Hello,

we bought a plot of land last year where our new building is currently being constructed. Today we received an invoice from the city for the "sewerage construction contribution" in the amount of 3715 euros. I already knew that development costs would arise at some point, but I have now read on the internet that the sewerage construction contribution is not part of the development costs and must be paid in addition. First question: Is that really the case?
Second question: According to the letter, the sewer was completed on 30.10.2008. Is it correct that we still have to pay the sewerage construction contribution now? The purchase contract for the plot states, "The buyer is aware that an amount between 15000 and 20000 euros will be incurred for the development of the object of the contract." But it says nothing about the sewerage construction contribution. Or does that then again belong to the "charges" that pass on to the buyer?

Thank you in advance for your answers!

That had to be done. The costs can still be charged years after completion. Mostly, municipalities wait until the last plot on the street is developed. And then issue the invoice.