How can I make an invoice if the hotel has not received the conference fee in advance?

Invoice in advance. Accounts received in advance, accounting enterprises in accordance with the provisions of the contract or the agreement of both parties to the transaction, from the procurement unit or labor service receiving unit in advance. Generally including advance payment, advance payment, etc. When the enterprise receives the money, the sales contract of goods or services has not been fulfilled, so it cannot be recorded as income, but can only be recognized as liabilities, that is, recorded in advance accounts.