The SENAF appertains to the Secondary Public Debt Market, managed by the Central de Anotaciones (Book-Entry System of the Bank of Spain).

According to the Spanish Stock Market Law:

"Official secondary stock markets are those which operate regularly, as provided in this Law and in its development regulations, and, in particular, regarding access conditions, admission to trading, operational procedures, information and publicity.

"The following will be considered official secondary stock markets:

	The Stock Exchanges.
	The Public Debt Market, represented by book entries managed by the Central de Anotaciones (Book-Entry System of the Bank of Spain).
	Markets of Futures and Options, for any underlying asset type, financial or non-financial.
	Any other market of national scope which, satisfying the requisites established in Section 1, will be authorised within the framework of the provisions of this Law and of its development regulations, as well as those markets of Autonomous Community scope which will be authorised by Autonomous Communities with competence on the matter."

In 1998, the fixed income market of the AIAF (Asociación de Intermediarios de Activos Financieros, Association of Financial Assets Intermediaries) was recognised as an official organised market.

On 23rd February 2001, the SENAF was granted the category of Organised Trading System (S.O.N., Sistema Organizado de Negociación).

Trading in the Secondary Debt Market can be performed via three systems, of which the first and the second are restricted to members of the market.

	Via the SENAF, directly or through a blind broker. Only Public Debt dealers can have access to this system. Trading is done electronically, with no knowledge of the counterpart. It constitutes the core of the Public Debt market, since the agents who participate in this segment commit themselves to quote Buy and Sell prices with reduced differentials, ensuring liquidity for the market as a whole. In this market only maturity operations are allowed, in cash or in instalments. Double operations are permitted. The settlement of losses and earnings is done daily with the market prices of the day, and on expiry of the operations the pertinent adjustments are made.
	The bilateral trading system, direct or through a broker, also called "second step", through which the rest of the trading between Account Holders is performed. The support of this market is the SLBE (Servicio de Liquidación del Banco de España, Bank of Spain Settlement Service). Maturity operations and double operations are permitted.
	The third and last trading system includes the transactions between the Managing Entities and their clients.