How much amount can we transfer from India to the USA? Is the limit per year?
As I understand your father in law is Indian Citizen and his tax paid earnings need to be transferred outside of India.
Under the Liberalized Remittance Scheme by RBI, one can transfer upto 2,50,000 USD. Please check with your Bank for the exact paperwork. A form 15CA and 15CB [by CA] are required to establish taxes have been paid.
What documents we have to present to the bank?
Should money be transferred to company's account(Indian Company) to USA company? or can be transferred to my husband's account.
Transfer of funds by a Indian Company to US Company has some restrictions. Please check with CA for details. If you father in law has sold the Indian Company and paid the taxes in India; he can transfer the proceeds to his son in US as per the Liberalized Remittance Scheme.
Can they just gift the whole amount to my husband? What will be the tax implication on my husband's part in USA and on my father in law in India.
The whole amount can be gifted by your father in law to your husband [his son]. There is no tax implication in India as being an Indian resident, gift between close relatives is tax free. There is no tax implication to your husband as he is a US Citizen and as per gift tax the person giving the gift should be paying the applicable taxes. Since the person gifting is not US Citizen; this is not applicable.