1. Go to Payroll, Setup, Employees.
2. Click List, select the employee, and click OK.
3. Press the TAB key, then click Taxes.
4. Find the tax id you want replaced, in the Recip Tax ID column enter the Tax ID you want to replace this tax to.  
5. Click OK, Accept table, Save, Close.

Note: It is not necessary to change the Adjustment Method to Replace.  If you are changing the Employee Reciprocity Agreement and no longer want a tax replaced to another tax, remove the tax id from the Recip Tax ID column.