Kailash Kumar,
If a previous payment is pending, a polite reminder message should be sent to Timmy Sir on the page where the payment is mentioned and where you upload your invoice for it. You could also then raise a separate forum thread about the pending payment if there is no response from him/payment is not made despite the reminder. If you mention it here, which is a payment announcement thread, it gets lost in the responses and may not be seen at all.
Note that it is advisable to bring a delayed payment to the notice of the admin. if you do not get the payment within at least a week of the submitted invoice. Please do not wait for so long to alert them.
When you make a commitment, you create hope. When you keep a commitment you create trust! ~ John C. Maxwell