I agree with Susan on this. We do our best to locate ratepayers.
For those of you with high volumes of returns like the City, I find it quick and easy to scan the barcode on the returned notices and bulk upload a Returned Notice code to the assessments. That done, we can quickly identify things like 603’s issued, properties sold, accounts paid, or addresses updated between the data extract and the notice return date to reduce the amount of follow-up required.