So..I recently received a letter from the council requesting a payment for council tax on the property my ex partner shared with his house mate. I immediately called the council to let them know that I myself had never lived at the property, though the occasional letter of mine did get sent to that address due to staying there during the week. You can imagine my surprise when they informed me that they in fact had a tenancy agreement signed by myself and my ex partners son, who also never lived at the property.
I have proof of residence at another property during this time, and was registered on the council tax at this other property until about 2 months ago when I moved into my own place. I called my ex to see if he knew anything about this and he then contacted the landlord of the old property, the landlord admitted that he had lost the original tennancy agreement signed by my ex and his housemate and that instead of footing the bill himself he had forged mine and his sons signature on a new tenancy agreement and sent that into the council office.
I know that what he has committed is fraud but I wonder what is the best way to deal with this issue? Do I wait until I am summoned to court with regards to the council tax bill and show my evidence or do I take him to court myself? Also would I be able to sue this guy for harassment or defamation of character?

