First of all, If the money given to you is within the period of 6 months: if such deposites are visible in the 6 months statement, only then you gonna need a gift deed otherwise its not mandatory.
For example: if you got the required amount from your Dad somewhere in Jan or Feb 2019 and you're expecting ITA in July, then Obvisouly you will have to prepare a gift deed regarding those transactions, as it is within the 6 months, due to which your average balance is affected.
However, if you're expecting ITA in August, then you won't be in need of any gift deed. Because your average balance for 6 months will remain same.
So, in case you got the money from your father before 6 months, you're good to go without any gift deed letter!