My ctc is 13lpa , with inhand 1lac per month but I heard this much inhand we get at 15lpa,but now during switch should I tell my inhand also

Hope you are aware about the tax bracket and how it works.

It is because they are not considering your previous organisation salary and due to that they are not deducting taxes i believe. Also now in new tax regime till 12.75 lakhs of income is tax free so after standard deduction and other deductions if it becomes 12 lakhs annually then you will get 1lpm