NaPO4 does not need parentheses here, but your equation isn't balanced; Sodium phosphate is an ionic compound and thus the charges of the individual ions must be considered. The formula is Na3PO4. Since this is the Undergrad Chemistry forums, I assume you know why parentheses are needed in some cases with ionic compounds...
Had you been writing a net ionic equation for this reaction, parentheses would not be needed as any subscripts would have been moved to being coefficients of the ion.
I hope this helps and I'm sorry if my answer is kind of nonsensical.
It's kind of late where I live