In what way did darius i ensure that the satraps actually sent the central government the wealth of the peripheral provinces?

Darius reorganized his empire by dividing them into twenty provinces called the "satrapies," headed by leaders, picked by Darius himself, called the "satraps."

A secretary was assigned in each of the satraps to observe the state affairs and communicate the events with Darius, while a garrison commander was responsible for the troops. A commission was responsible for the evaluation of the expenses and revenues of each of the satraps, while a treasurer safeguarded the provincial revenues. More importantly, a network of royal inspectors called the "EYES AND THE EARS OF THE KING" were established by Darius to do further checks on the satraps.

Dpolitical is the answer