I think the bit that everyone seems to forget is the word tax this is a government tax collected locally. The powers are far and wide and frankly having worked for them at times terrifying.
As @plumpuddisnice has said, those of who have worked in council tax and business rates know something weird has gone on here. The OP needs to speak to CAB because someone has been liable on that account for 7 years, maybe not paying anything but definitely liable, named and the bill sent every year with it saying if there is any change you need to let us know.
There are set procedures for the bill, when it is sent out (every year) the fact that it is a 10 month arrangement rather than 12, if you do a weekly payment plan for your current ctax year it is confirmed by letter and they have to send a letter accompanying this to say that this is a deviation from the standard 10 months as it is all legislation based. The whole bill, reminder, final reminder (full balance due) summons to court is all the same across the country or it was when I worked there.
Once that summons goes out to you to summon you to court we were allowed to agree a payment arrangement but only with the Liability Order going through (what the court grants).
That is the far reaching piece the council need to go guns blazing. This grants them to either take it directly from your earnings or send in the bailiffs. The Attachment of Earnings order is a set percentage and they can take 2 years previous council tax at the same time. Here is how much they can take, this is not who I worked for just the first google hit but honestly, always pay your council tax www.northampton.gov.uk/info/200028/council-tax/996/council-tax-attachment-of-earnings
As an example for the non-link clickers if your net weekly earnings are exceeding £225 but not exceeding £355 they can take 12% straight from your salary but they can issue 2 orders at once so they take more money. They want it in and want it in quickly.
I will say that as an employee we would bend over backwards to help people, there is a difference between can't pay and won't pay. Can't pay we do everything we can. Won't pay, you need to change your priorities bill wise.