Dear …
RE: Lease: __(address location)__ to __(Name of Company)__ Expires: __(Date)__
Over the last __(# years)__, we have been very fortunate to have had __(you/name of company/etc.)__ as a tenant at __(name of building/location)__. We regret to inform you, however, that __(name of organization)__ is not in a position to offer renewal of your lease on __(date)__. As with most businesses, it was apparent that eventually, we would outgrow our own premises and have to expand into additional space. That time has now come.
__(Name of organization)__ has reached the stage of growth where we have found ourselves in critical need of more space. After researching all of our options, it has become evident that our most practical option is to expand into the location that __(you/name of company)__ currently __(occupy/occupies)__. It is difficult to have to inform a tenant of such a situation and we apologize for the inconvenience this will cause you. Regrettably, our own business growth dictates the necessity of this.
Your current lease will expire on __(date)__. It has been a pleasure to have you as a tenant and we will be pleased to provide you with a Letter of Reference if required for your future lease negotiations.
Yours truly,