Do I understand correctly that you only need a new application if you want to change the funding level or want to use the now higher loan amount?
We received a KfW55 approval (100,000€) at the end of last year. So far, the architect meeting with the general contractor has not even taken place.
However, I do not want to touch the loan again since we got it at 0.45% (instead of 0.75%, special promotion by the intermediary bank).
According to the KfW information sheet:
"The repayment grant is calculated based on the approved amount valid at the time of recognition of the 'confirmation after completion' and is credited to the last installment due according to the repayment plan (shortening of the loan term with constant annuities)."
That means you automatically receive the new grant of 15% (for us 15,000€ instead of 5,000€) with KfW55.