I have sold holiday package to client worth Rs.200000 and received Rs.20000 as down payment and remaining amount will be collect in 36 installments how do I pass these entries in tally.

You create a debtors account for the 200000 debit debtors (client name) credit sales, You record the deposit 20000 credit debtors account debit cash and as each installment is collected; credit debtors account debit cash.

If you are working purely on a cash basis you might want to record the cash received as sales when you receive it but the first suggestion is the correct approach.

No doubt you will need to send the debtor an account each month showing the amount to be paid and the outstanding balance

Much of this is dependent on whether the package is for some future date or will be taken soon and paid later