Walking away or posting the keys through the letterbox is called 'abandonment' and will not end your agreement. Your agreement with the landlord will continue even though you've left and the landlord can continue to charge you rent, so you're likely to build up rent arrears: if your agreement is fixed term, you can be charged rent until the term ends if your agreement is periodic, you can be held liable until the agreement could have been ended by giving proper notice. The landlord can apply for a court order to make you pay what you owe. The court will decide whether you should have to pay your landlord the money or not. The landlord may have to show that s/he has tried to find another tenant for the property but hasn't been able to do so. If the landlord has managed to let out the property they can't claim rent from you after the date the new tenant moved in. If the landlord doesn't make any effort to let out the property the court is likely to reduce the amount of money you will have to pay.
This may be possible if you have no choice but to leave early and want to avoid paying rent on more than one home. However, you have to get the landlord's agreement for the person you suggest to move into the property. The landlord may want to take up references for them.
There are only limited ways in which this can happen; the landlord cannot make the tenants move out, nor can the tenants lawfully walk away from their contractual obligations. Either party might request of the other that a formal surrender of the tenancy be allowed. It would then be up to the parties to agree the terms and conditions of such a surrender. This might include some financial compensation for inconvenience or costs incurred.
You have a joint tenancy if you share with a spouse, partner, family member or friend and both/all of your names are on the agreement. The actions of each individual person will affect all of your rights. For instance: If one of you gives notice to the landlord, the agreement will normally automatically be ended for all of you. None of you will have the right to continue living there. However, this does not apply if you have a fixed term tenancy that has not come to an end. If one of you leaves without giving notice, the whole rent will still be due and the other(s) will have to pay the missing person's share. If one of you has caused damage, the landlord may be entitled to take money out of your shared deposit. If you're thinking about leaving, be sure to discuss it with the other joint tenant(s) before you take any action. It may be possible for someone else to take your place, and/or for the landlord to give a new agreement to those who are staying.
If a Landlord wishes to gain possession, they must give a minimum of 2 months’ notice in writing to end at the end of a period. If you wish to give notice, you must give a minimum of 1 months’ notice in writing to end at the end of the period. Definition of a period - e.g. if your tenancy commenced on the 5th of a month, the notice will expire on the 4th.
The law around ending a tenancy is relatively straightforward as long as the right timescales and procedures are followed, along with the use of the correct format of notice. It is recommended that you end your agreement properly if you want to leave. If you don't you may still be liable to pay rent, even after you've moved out. To do this, you have to give written notice to the landlord. You may not be able to end the agreement early if you have signed for a tenancy for a fixed period of time.