I own a flat that I have lived in with a friend for one year, who has just moved out. Just as we moved in he lost his job, and has had difficulty finding a new one. On a number of occasions I let him off on paying rent until he had the money, and he did not actually pay a deposit until half way through the tenancy. As he has come to leave, he has been increasingly pushy about wanting his deposit back. I have no intention of keeping it, but as he requested his deposit on the day that he moved out, I said that I wanted to hold onto it until we had received all the final bills, which he is obviously not very happy about. He received council tax benefit, and at one point during the year this was revoked, he was certain that he was entitled to it, so told me that he was in contact with the council and was dealing with the situation. I was working away as my job involves frequent travel, and on my return he told me that we had incurred court charges due to not paying the council tax, which I believed he was dealing with. I paid off these charges. On his moving out, he said that he had spoken to the council and was entitled to a rebate, and told me that I would be receiving a letter detailing this. I didn't receive a letter, which he then said had been sent his address, but that he required me to sign, I found this strange if this was his rebate that he was entitled to, why would I be involved, when I spoke to the council the said it was a rebate for us to distribute as we agreed on. He states that he believes he paid me a full amount of council tax, when actually he had a discount and therefore was not liable to pay. My question is how is the discount applied, if we are both named on the account, is it strictly his discount and is he entitled to the full rebate?

As a lodger he would not be liable for Council Tax nor eligible for Council Tax Benefit. The person living at the property who is highest on the Council Tax liability hierarchy is the one who should be on the Council Tax account. As you are the owner occupier that is you. People should only be held jointly responsible for Council Tax by the Council if they are on the same standing i.e. joint owners or joint tenants. If he has been given Council Tax Benefit it would appear he has put himself down as a joint tenant rather than a lodger.

Landlords for lodgers usually include an amount for Council Tax in the rent. He should have applied for Local Housing Allowance/Housing Benefit if he was on a low income and couldn't pay his rent.

I'm not really understanding the last part. Did he give you any money towards the Council Tax bill? If so did it cover his amount? Has he been given money (Council Tax Benefit) or has it been paid directly into the Council Tax account?

Aviva is spot on - your friend is not entitled to any council tax benefit. As the resident owner you remain liable for the council tax charge due on the property.