Government Debt exchange auctions are a discretionary formula used by the Treasury to withdraw from the market certain references, replacing them with others. 
The main aims the Treasury pursues through its exchange programmes are:
  1. To rationalise the structure of government debt maturities by eliminating illiquid references with little residual life.
  2. To alter the maturities curve of outstanding debt, lengthening or shortening it
  3. To ensure that enough strippable bonds are outstanding in order to ensure that Bono and Obligación stripping and reconstitution operations are backed by sufficient liquidity.
  4. To build up the liquidity and depth of the Public Debt market, in order to attract investor savings within the single capital market defined by European Economic and Monetary Union, and ensure the Spanish Treasury can successfully compete with other sovereign issuers.