What is the correct net ionic equation for the neutralization of phosphoric acid? What is the net ionic equation for the reaction between phosphoric acid and sodium hydroxide? 

I came up with
\begin{align}
\tag1 \ce{H+ + H2PO4- + OH- &amp;-&gt; PO4^3- + H2O},\\
\tag2 \ce{H+ + OH- &amp;-&gt; H2O}.
\end{align}

Or is it, since phosphoric acid is a triprotic acid, whose ionization is 
$$\ce{H3PO4 &lt;=&gt;3H+ + PO4^3-},$$ 
therefore the net ionic equation will be 
$$\ce{3H+ + 3OH- -&gt; 3H2O}?$$
Phosphoric acid dissociates into hydrogen ions and $\ce{H2PO4^-}$ ions in water.  This then can dissociate further, but $\ce{H^+}$ and $\ce{H2PO4^-}$ are the primary ionic species you'd find in a phosphoric acid solution.  

$\ce{NaOH}$ dissociates completely into $\ce{Na^+}$ and $\ce{OH^-}$ ions.

The reaction would then be between $\ce{H^+}$ and $\ce{OH^-}$, your option 2.  

The difficulty arises because adding more $\ce{NaOH}$ to the reaction pulls off the second then the third hydrogen from the phosphoric acid.  In all cases it is an $\ce{H^+}$ reacting with an $\ce{OH^-}$ ion with the phosphate ions as spectators, but that really doesn't tell the story of the reaction well.  This is a case where the net ionic equation really isn't your best option.emphasized text