This is the 13571st most frequent Russian word.
начальству
"Начальству" means "to the management" or "to the authorities" in English.
In this sentence, 'начальству' is used in the dative case to indicate to whom the report was submitted.
Я передал доклад начальству вовремя.
I submitted the report to the management on time.
Here, 'начальству' is also in the dative case, indicating who expressed displeasure with the project.
Начальству не понравился наш проект.
The management did not like our project.
The word 'начальству' is in the dative case, showing the direction of the expression of gratitude.