I owe thousands to the IRS for failure to file proper forms on time for business that never made a penny in profit. In fact the last time I mailed them in on time but they claim I did not. It's up to me to prove I did.
There is something wrong with this country and this story is an example.
Registered mail is the only way to deal with lying unprosecuted felons.
They'll blow that off as long as they can, also. Took them a week and a half to acknowledge a piece of registered mail from me, once.