No property tax notice received after house construction, reason?

Has he at least received the information for determining the unit value?

So, the normal procedure is as follows: The tax office is notified by the notary when a property is sold. This notification is then processed by several departments. Usually, the assessment office contacts you and asks what you plan to do with the property, the real estate transfer tax office wants money, and from the valuation office, you either receive an adjustment continuation or a retrospective determination. If the property is undeveloped and a building is constructed in the following year, the municipality/city then informs the valuation office. The valuation office usually sends a letter requesting a declaration. However, there are often problems here. Either something gets lost along the information chain, or, which is not unusual, the valuation office is hopelessly understaffed. The simple reason is that the officials are paid by the state but collect money for the municipalities. So let's say the valuation office was not high on the priority list of the departments for a long time. But that has, of course, eventually been rectified.. At some point, your buddy will receive mail; he should be prepared for the fact that the tax office can assess retroactively for four years.

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It is a mystery what went wrong there, but ...
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I am curious about the solution to the mystery ... :)

Did he at least receive the information to determine the standard value?

Only from the property. And they waive that.

So, the normal procedure is as follows: The tax office is notified by the notary when a property is sold. This notification is then processed by several departments. Usually, the assessment office gets in touch and asks what one intends to do with the property, the land transfer tax office wants money, and from the valuation office, one either receives a continuation of allocation or a subsequent determination. If the property is undeveloped and a building is constructed in the following year, the municipality/city informs the valuation office. This generally sends a letter and requests a declaration. Unfortunately, there are often hiccups here. Either because something gets lost along the information chain or because, which wouldn’t be unusual, the valuation office is hopelessly understaffed. The simple reason is that the officers are paid by the state but collect money for the municipalities. So let’s say the valuation office was not high on the priority list of the authorities for a long time. But of course, that has eventually changed. Eventually, your friend will receive mail; he should just be prepared for the tax office to make assessments retroactively for four years.

He can live well with the 4 years retroactive period. But does he not have to pay a penalty? Is it then the case that it is not his fault?

Real Estate Tax Act (GrStG)
§ 19 Obligation to Notify

(1) Any change in the use or in the ownership of a tax object that is wholly or partially exempt from real estate tax must be reported by the person who, according to § 10, is liable for the tax. The notification must be submitted to the tax office responsible for determining the assessment base within three months after the change occurs.
(2) The cessation of the conditions for the reduced assessment number according to § 15 paragraph 4 must be reported by the person who, according to § 10, is liable for the tax. The notification must be submitted to the tax office responsible for determining the assessment base within three months after the conditions cease to apply.