Cash receipt

Yes.

Cannot accept more than 2 lakhs cash as per sec 269ST. Penalty of equivalent amount under sec 271DA.

Yes, if you have carried Rs 2 lakh or more transaction in one single day, then you are liable to pay penalties which is 100% of the entire amount of cash received. 

Penalties on cash transaction is specified under section 271DA of Income Tax Act. The section says, if a person receives any sum in contravention of the provisions of section 269ST, he shall be liable to pay, by way of penalty, a sum equal to the amount of such receipt.

These penalties are imposed by Joint Commissioner. 

Thank u sir but one more doubt if i receive this cash in 4 diffrent days below 2lks per day any problem?

As Per 269ST, No person shall receive an amount of two lakh rupees or more—
(a) in aggregate from a person in a day; or
(b) in respect of a single transaction; or
(c) in respect of transactions relating to one event or occasion from a person,

As if you received this cash on 4 different day, but as it's "Single transaction" of sale of car, So, Penalty is applicable....

I sold 3 different cars...so will it be a single transaction ? what is meant by single transaction?

If you sold 3 Car to 3 different person sepratelly than it's 3 transaction...
If you sold 3 Car to single person in a "single deal", than its Single transaction..