First, people usually follow dissolution accounting. They will sell off the assets, clear the out the liabilities and the residual net worth, also known as equity is the value of the firm.
The measurement criteria for disposals is ‘lower of carrying amount or FVLCS’. If you browse through IndAS, you will find details of disposals in a separate standard- Non current assets held for sale. Another standard emphasises on- Disposal of subsidiaries.
The closing of the business for unlisted companies is same as dissolution accounting again, i.e., profit or loss from disposal after settling all liabilities is taken and settled off with owners capital account. If it is a loss, the owner usually will go bankrupt and vice versa. Eg: after settling off liabilities, a company is worth 1 Million. Purchased the business with .5 million. Then profit on disposal of business is, one million minus half a million minus capital gains taxes.