Judging from the existing rules of various countries, the tax rules of most countries are based on the basic premise that stock index futures trading is a sales contract, such as Germany, the United States, Britain, Australia and so on. However, there are differences in the identification of the transaction target. For example, Germany believes that the trading target of stock index futures is a highly abstract stock index, which cannot be delivered in kind, while Britain believes that the trading target is the rights and obligations in the contract. At present, there are many disputes about the legal nature of stock index futures contracts in domestic academic circles, including three different theories: "buying and selling futures", "buying and selling futures contracts" and "compromise". All three theories believe that the stock index futures contract belongs to the sales contract, but if the stock index futures contract is a sales contract, the result of contract performance is "the seller transfers the ownership of the subject matter to the buyer", and the income obtained from this should be "the income from property transfer". However, according to Article 8, paragraph 9 of the Regulations for the Implementation of the Individual Income Tax Law, "property" refers to "valuable securities, shares, buildings, land use rights, machinery and equipment, vehicles and boats and other property", while Article 16 of the Regulations for the Implementation of the Enterprise Income Tax Law stipulates that "property" includes fixed assets, biological assets, intangible assets, shares and creditor's rights. According to the theory of "buying and selling futures contracts", futures trading is the auction of futures contracts in special places, that is, the general transfer of rights and obligations of futures contracts, which seems to belong to "creditor's rights" in property. However, although there is no clear definition of "creditor's rights" in the Implementation Regulations of the Enterprise Income Tax Law, the "creditor's rights" in the tax law do not have the same connotation and extension as the creditor's rights in the civil law, but only refer to the rights arising from monetary lending in the traditional sense. Therefore, although according to the civil law, stock index futures contracts contain creditor's rights, it is still difficult to be classified as "creditor's rights" in the tax law. In fact, whether stock index futures trading belongs to "contract trading" is still in doubt. From the actual transaction process, investors' opening position is the conclusion process of forward delivery contract, while hedging and closing position is to write off the original contract by concluding a new futures contract with the same quantity and the opposite direction. Investors didn't transfer their own stock index futures contracts, but because they hold two contracts with the same number and opposite directions at the same time, the performance of the new contract can just ensure the realization of the original contract, and the interests of all parties can be realized through the settlement system, thus ending the obligation of investors to participate in delivery and liquidation. Therefore, stock index futures trading is not "contract trading".

According to the viewpoint of "buying and selling futures", stock index futures trading is the behavior of traders buying and selling stock price index by concluding standardized futures contracts, and its subject matter is the stock price index compiled in a certain way and its ups and downs. The stock price index is a virtual non-physical economic symbol, which has no value in itself, so it seems difficult to classify it as "property" in the income tax law. Some scholars believe that although the stock index cannot be delivered in futures trading and can only be settled in cash, it can also become a "thing" in trading as long as it is legally recognized as a "fiction". But as the scholar emphasized, a virtual thing can be made into a legal thing, and it must be a real and realistic right, which can bring tangible benefits to the obligee. Stock index is an objective set of data, and its rise and fall are only related to the changes of some stock prices. In fact, it is still not dominated by manpower, so it is difficult to set any rights that can bring certain benefits above the stock index. Therefore, the stock index is not "property" and is not the object of stock index futures trading.

Stock index futures trading is based on the need to manage and avoid systemic risks. The purpose of participating in stock index futures trading is to undertake, transfer or manage certain risks with certain monetary investment. In this trading activity, the stock price index is only a reflection of the risk of the development and change of the stock market at a specific time in the future, or a carrier. The stock price index basically represents the trend and range of stock price changes in the whole market, and the stock price index at each time point reflects the risk of the stock market at that particular time point. This risk can be quantified as monetary value. Although the stock price index is a virtual existence, the risk it represents is real and can be expressed in money. The conclusion of stock index futures contract is not to realize the transfer and possession of stock value index, but to obtain the opportunity to avoid or bear specific risks at a specific time in the future through the conclusion of the contract. Therefore, stock index futures trading is actually an agreement on the transfer and commitment of future risks at the expense of a certain currency, and its target is the risk management right in a specific period. One party of the transaction transfers the risk management right, so as to get the corresponding reward, and the other party obtains the risk management right and pays a certain fee. In this kind of transaction, the stock price index is not the object of both parties' transactions, just like other financial products, it represents a specific type of market risk. The transaction price of stock index futures reflects the degree of future market risk changes and the value of risk management right determined by it. Therefore, the stock index futures contract is a trading contract with "risk management right" as the subject matter, with the stock price index as the reference, reflecting that its value changes with the change of the index. With the transfer of risk management right, the corresponding property between the parties has changed. The risk management right based on the stock price index is also a "property" that can bring tangible benefits to the obligee, and the increase or decrease of property caused by its transfer between the parties should have the effect of tax law. Stock index futures contract is a standardized agreement made by futures exchange, and it is the object of stock index futures trading. Generally speaking, stock index futures contracts mainly include the following elements:

(1) contract object. That is, the basic assets of the stock index futures contract, such as the Shanghai and Shenzhen 300 stock index futures contract is the Shanghai and Shenzhen 300 stock price index.

(2) Contract value. The contract value is equal to the product of the index point of the market price of the stock index futures contract and the contract multiplier.

(3) The quotation unit and the lowest price change. The quotation unit of stock index futures contract is the index point, and the minimum change price is the minimum change range of the index point.

(4) Contract month. Refers to the month when the stock index futures contract is due for delivery.

(5) trading time. Refers to the time when stock index futures contracts are traded on the exchange. Investors should note that there may be special provisions on the trading hours of the last trading day.

(6) price restrictions. It means that the fluctuation range of the trading price of a futures contract in a trading day or a certain period of time shall not be higher or lower than the prescribed fluctuation range.

(7) Margin for contract transactions. Contract trading margin accounts for a certain proportion of the total contract value.

(8) mode of delivery. Stock index futures are delivered in cash.

(9) The last trading day and delivery date. Stock index futures contracts shall be settled in cash on the delivery date, and the specific arrangements for the last trading day and delivery date shall be implemented in accordance with the provisions of the exchange.