This article explains how to create a filter for specific postal codes in Access HandiTax.
To filter reports for specific postcodes
Go to Report, Client, Client List Abbreviated.
On the Client Expression window, click New.
Give your expression a Name and in the Expression field type in the following: (HasText(GetPostalAddress(Ref@Clients,"2"), "6000"))
"6000" can be replaced with the postcode you are filtering for.
Click Save, then Select to run the expression.