Hi,It is worth considering the following points:
1. Your current resident Indian savings bank account cannot be changed to a Non Resident External (NRE) account. This is because NRE accounts are simply intended to assist you in saving your income from abroad. According to the SBI NRI FAQ page, “You can re-designate your existing account into NRO account.
2. In order to convert your account, please request/check on the banks website for a standard request letter For converting resident Indian savings bank account into NRO savings bank account on change of residential status and post / courier/email it to your home branch along with supporting documents mentioned in the letter..
3.Though nothing is clearly mentioned regardimg the time limit for converting the account . However continuing to hold your resident savings account after gaining NRI status is considered illegal under the Foreign Exchange Management Act (FEMA) guidelines and doing so may attract hefty penalties. Under the Act, any individual who fails to adhere to the guidelines is liable to pay a penalty of up to 3 times the amount involved in the existing resident savings account or Rs 2 lakh when the sum is not quantifiable. Additionally, a penalty of Rs 5,000 is to be charged every day from the first day of intervention until the penalty is paid.”
Keeping in view the above I shall suggest you to initiate the process at the earliest even if there are no clear guidelines regarding the matter , but why take chances if it is as simple as sending an email with the requisite proofs.
Thanks