So if you have been claiming housing benefit since before 1/1/1996 you don't have to pay it and are due a refund if you have been paying it.

How do you pay a tax that doesn't exist?

Nobody pays anything, never have never will.

What has happened is an adjustment has been made to housing benefit claims. I wish people would get this thing clear in their minds.

Here is a quote from the announcement
"3.For claimants to come within paragraph 4(1)(a) of Schedule 3 to the Consequential Provisions Regulations, they must have been continuously entitled to HB since at least 1 January 1996 and occupied the same dwelling since that date, save for any period where a fire, flood, explosion or natural catastrophe has rendered the property uninhabitable"

This does not apply to everyone so there is still a "tax" that has to be paid
You are right saying it is not a tax (also known as Spare Room Subsidy) but we all know it really is
The "bedroom tax" label has stuck so lets just say it is a tax

Like a broken record.

and in the meanwhile..... up to 40 000 people can expect reimbursement due to the sheer incompetence of IDS and the DWP