Averill is right – if your lease has validly expired, and you are negotiating with the landlord for a new lease, the landlord can dictate the terms and the rental rates, just as it can decide not to lease at all. If the landlord is seeking rent that is above market rates, it may think that it will be able to achieve that rate (if there is, relative to demand, a lack of that type of premises in your area, that may be the case), or it might be aware that you don’t have an alternative and are using that as leverage. Regardless of the reason for their approach, there is no protection for commercial tenants at law that prevents a landlord from taking that approach. Commercially, you could choose to call their bluff and advise that you are not willing to lease on those terms in the hope that they will soften their terms, but if that does not work it will see you without premises. You may want to engage a commercial real estate agent to give you some advice on what other premises are available and the current state of the rental market.
From what you have said, it seems your lease term had expired when they bought the premises, that you were “holding over” on a month-to-month basis, and that they then gave you notice ending that “holding over” effective at the end of March. As Averill notes, there may be scope to argue that valid notice wasn’t given, but we would need to look at the correspondence on that to advise.
You mentioned also that you have paid some rent but they are trying to stop you from trading. What period was the rent that you paid for? What are they doing to stop you from trading? Again, you may have an argument that there has been agreement to allow you to stay beyond March while you negotiate but again it depends on the context and correspondence.
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