Joining a new company without resignation from previous company

Hi, I am currently working with tech mahindra and has been selected in mattsen kumar for same position. I would like to move due to good salary however, if I get hight salary in my current organization so I will stay with the same organization and deny for new offer But the thing is that I did not get the confirmation from my manager neither for immediate releasing bor for salary increament as the discussion will happen on Monday and then he will discuss with associate director. On the other hand the hr of new company has sente the offer letter for today's joining but I informed her that the resignation may happen on Monday So she is asking me to submit all the required documents and joining as well as relationship declaration form on her personal email id stating that it will take time to verify the documents as well as I m the last candidate left due to which the whole batch is pending. So meanwhile she will check and then to save the time of documentation and then on. Monday after getting the resignation acceptance letter she will proceed further. Whereas resignation acceptance letter is as mentioned as "if applicable" In the offer letter So as I understood it may be considered as joining and if I deny to join later and continue with my same organization so it may a problem for me. Pls confirm the same whether it is fine to send the documents before or not even I am still on my current organization.