Why are some collection accounts not listed on credit reports

[Anonymous]

Hi, I have a general question about collection accounts and why some collection accounts do not appear on my credit report anymore.  I have a few accounts I know to be in collections that are a few years out from charge off and they dropped off my credit reports.  I still occasionally get settlement offers on them in the mail.   I realize that they are frequently sold, but why wouldn't the new collection agency post them with the bureaus?  Do they have to pay the bureaus to do so?

Thanks!

[FireMedic1]

If the old CA sold it to another one and it isnt showing up. It will in time. Or. Thank your lucky stars it isnt and have a glass of wine.