Setting an item tax code

Hi,

When creating an item (e.g. ServiceSaleItem) the tax code must be specified, as the following message says:
Status detail: ERROR, USER_ERROR, Please enter a value for Tax Code

To set the tax code I am using the following code:

        ServiceSaleItem item = new ServiceSaleItem();
        RecordRef rr = new RecordRef();
        rr.setType(RecordType.???);
        rr.setInternalId("0");
        item.setSalesTaxCode(rr);

My question is what RecordType should be used? In the RecordType class I can find the following types related to taxes (there is no _taxCode or _salesTaxCode):

_salesTaxItem
_taxGroup
_taxType

Thanks,

Gaetan