Partner program payment of march month haven't still came to my account. It has been 5 days.
If you are talking about the payment of earnings if you reached $100 (or more) by March 31st the new rules are iStock/Getty will pay you by April 25th.
If you are talking about partner program sales for the month of March being reported then that can happen at anytime during April iStock/Getty only advise the reporting will be completed before the end of the following month (April 30th)