How does one handle IRS and other tax liens on Suppliers? Best Practice?

We receive demand letters from both the IRS and state tax department to withhold percentage of payment from individual tax payers that have not filed or paid their taxes. In essence, we are required to send funds to the IRS if AP payments are made to them. Historically this has been done by adding a second location to the supplier with a remit to address of either state tax department or the IRS. The other locations are inactivated until we receive a release letter. This becomes problematic for a couple reasons. First, the IRS rarely sends release letters so we keep garnishing until the supplier