Wait with the building application because of the child construction allowance

From the KfW homepage:

"Under what conditions do I receive Baukindergeld for my child?
For all children who meet the following funding requirements on the day of application, you will receive Baukindergeld for the entire payment period:

the child is already born and under 18 years old,
the child lives with main residence in your household (registration certificate), and
you or your partner living in the household are entitled to child benefit for the child."

It is always only the day of application that is referred to as the key date. Nowhere do I read that the child must already be born at the time of moving in.
The same applies to income limits and allowances per child. The decisive factor is the status quo at the time of application.

Yes, that's right, you get the Baukindergeld for all children who are registered on the day of the registration confirmation!

But eligibility also depends on your income tax return from 2017 and 2018. If you exceed 90k€ zvE with one child there, you are out. Since back then there was no 2nd child and therefore the 105k€ zvE for the average from 2017/2018 does not apply.

In other words, in 2017 and 2018 I am below 90k€ with one child, and my wife becomes pregnant with quadruplets, then there are 5x 12k€.

If I am over 90k€ with one child and then get quadruplets, there is nothing.

Yes, that's right, you receive the Baukindergeld for all children registered on the day of the notification confirmation!

But eligibility for funding is also based on your income tax returns from 2017 and 2018.
If you exceed €90k taxable income with one child, you're out. Since there was no second child back then, the €105k taxable income threshold for the average of 2017/2018 does not apply.

In other words, in 2017 and 2018 I was under €90k taxable income with one child, and my wife becomes pregnant with quadruplets, then you get 5x €12k.

If I am over €90k with one child and then have quadruplets, there is nothing.

To my knowledge, the income limits apply based on the number of children at the time of application. This means that even if the child or children are born two weeks before the application, they count toward determining the income limits also for the years when the children did not yet exist.
There is a good website where many such questions can be clarified. Just use a major search engine and enter some keywords like: questions about Baukindergeld.

As far as I know, the income limits apply based on the number of children at the time of application. That means even if the child/children are born two weeks before the application, they count towards determining the income limits, even for the years when the children did not yet exist. There is a good site where many such questions can be clarified. Just start a big search engine and enter a few keywords, after all, you have: fragen zum baukindergeld

Or just call and ask! That’s how I understood it! Otherwise, the 2017 and 2018 tax returns could be arbitrarily swapped by date, plus the children or non-children with allowances and all that are also listed there.

Yes, that's right, you receive the Baukindergeld for all children who are registered on the day of the registration confirmation!

But the eligibility for funding is also based on your income tax returns from 2017 and 2018. If you exceed the 90k€ taxable income threshold with one child, you are out. Since there was no second child back then, the 105k€ taxable income threshold for the average of 2017/2018 does not apply.

In other words, in 2017 and 2018, I was under 90k€ with one child, and my wife gets pregnant with quadruplets, then there are 5 x 12k€.

If I exceed 90k€ with one child and then have quadruplets, there is nothing.

I am not an expert but I am quite sure that you are wrong. I have never read it like that anywhere.

Or just call and ask! That's how I understood it! Otherwise, the 2017 and 2018 tax returns would be arbitrarily interchangeable by date, plus it also shows whether there are children or non-children along with allowances and such.

Which tax return is used does not change because of that. It is only about what income limits are applied. And as far as I know, all children are considered at the time of the application.