The ionic equation for the reaction between HClO4(aq) and NaOH(aq) to produce H2O (l) and NaClO4(aq) is:

H+(aq) + ClO4-(aq) + Na+(aq) + OH-(aq) → H2O (l) + Na+(aq) + ClO4-(aq)

In this equation, the spectator ions, Na+ and ClO4-, are omitted for simplicity. The net ionic equation is:

H+(aq) + OH-(aq) → H2O (l)