When Does A Notice Period Starts?

Hi,
I am currently working in a Indian MNC, I put resignation recently but my line manager and his line manager are accepting my resignation. In my company the resignation is done through SAP. So I put my resignation on SAP to my mangers and HR as per the procedure. After that I sent a hard copy system generated resignation letter with duly signed to all concerned.
My question is, When I ask my HR about the notice period she said the notice period starts from the day I Put resignation and she told it has nothing to do with SAP approval. As SAP approval meant for due clearances.
Please clarify me when does an employee's notice period starts???? the day he submits the resignation??

Notice period starts from the day when you give resignation letter. Depending upon your firm's policy calculate the period from that day onwards. Some have one month, others three months period policies.
The period includes holidays, leaves taken by you.

As per my knowledge, Your notice period stars when your resignation accepted by your respective reporting manager on hard copy or via mail. For SAP approval, once your reporting manager accept your resignation then you need to put request in SAP.

As per my experience the Notice Periods starts from the Day One you put the resignation, if you don't get the acceptance mail then do follow up with the respective head, may be they would be busy but try to convince to give you the effective date.

Notice period starts, the moment you get acceptance for your Reporting Manager/Approving authority.. It may go via sap or hard copy, will not make any differecnce.

The day you submit the resignation your notice periods starts. However based on the tasks you responsibly need to complete, the last day will be intimated to you on agreement by both the parties. But in your case, I think your HR has already cleared your doubts. She has answered you as per the company policy. Then what and why are you worried about?
Let alone SAP.

The day when an employee puts his/her resignation the loyalty factor diminishes from that day, hence the resignation date/date of sending the resignation will be counted/taken into account.
With regards to your query where is the hiccup do you want to stay more i.e. the difference of day from the actual resignation and its approval, kindly clarify so accordingly members can revert back.