That's right, they're dead!
I have been doing "skip tracing" on bounced (invalid address) mailings I have sent. On one of these the new mail came back marked
DECEASED 5 years ago
So I started looking for more of these in the data and the records seem to have plenty, including one guy that I found this evening that died in 2014!
So I've started writing to these addressed to "Estate/Next of Kin of [the non-taxpayer]."
I just have sent out 4 of these the past few days, but I envision that this should return more like a 20% or better response rather than 3-5% for the normal "alive" contingent ...
By the way, my skip tracing tool is Whitepages.com, which works well and is only $5 per month for up to 20 searches.
More next week ...