Hi Pawan,
from RE-FX perspective you can trigger the posting of the due cashflow items already some days earlier if you select the due date accordingly in the periodic posting run and create the open items in FI in advance so that there is enough time to handle the payment process.
The payment itself is created with the payment run (transaction F110) in component FI. The payment run decides if an item is processed or not using the next payment date.
If you have more detailed questions about the payment process and F110 I would suggest to open a thread in the Financials area.
Regards,
Franz