The final decision on who receives shares in an IPO.
After an issue closes, the registrar works out the basis of allotment with the exchange. Under SEBI's T+3 timeline this normally happens on the first working day after the close, and shares are credited before listing on the third working day.
Allotment status is checked on the registrar's website or the exchange site with a PAN or application number. A genuine check never asks for a payment or a password.