Following the investiture of Manuela Carmena as Mayor of Madrid on 13 June 2015, Sánchez Mato entered the City Government Board, holding the Area of Economy of Finance of the municipal executive.

[6] During his time as Councillor of Economy and Finance, Sánchez Mato clashed with Cristóbal Montoro, Minister of Finance, and, ultimately, also with Manuela Carmena, regarding the rule of spending imposed from the National Government and the Economic Financial Plan (PEF) for the municipality that, through austerity measures, constrained the budgetary plans initially envisioned by the City Council.

[8] He was then re-shuffled to the Presidency of the district of Latina, a position he effectively assumed on 12 January 2018, replacing Esther Gómez Morante [es].

[9][10] In early March 2019 Sánchez Mato announced his intention to run in the IU primaries to select its candidates to the April 2019 general election in the Madrid constituency within the Unidas Podemos coalition list.

[11] Following the renouncement of Mauricio Valiente to led IU in the primary election of the Madrid En Pie coalition for the list to be presented at the 2019 Madrid municipal election, after the membership of United Left–Madrid (IU–Madrid) decided in a referendum not to run in the Unidas Podemos coalition for the 2019 Madrilenian regional election (in collision with the federal board's stance), Sánchez Mato accepted the responsibility of replacing Valiente on the condition the IU board tried their best to finally include Podemos in some form in the regional tentative candidacy,[12] then visibly led by Sol Sánchez (IU–Madrid) and Raúl Camargo (Anticapitalistas Madrid).