Nairobi, April 26 -- When Lilian Nyawanda picked up the call on April 8, she knew instantly that her career had entered a defining stretch.

On the line was the chairman of the Kenya Revenue Authority (KRA) board, Ndiritu Muriithi, informing her that she had been selected to serve as acting commissioner-general following the abrupt exit of Humphrey Wattanga.

The appointment, pending a substantive hire, placed her at the helm of one of Kenya's most consequential institutions, mid-financial year, with revenue targets looming.

The tax authority had by the end of March collected Sh2.038 trillion by the end of March-the first time it had crossed the Sh2 trillion mark within nine months. But that meant the authority was facing an almost impos...