I have a commercial office tenant in California who is not paying rent. I plan to post a 5 day to Pay or Quit. Do I just include rent amount on the notice or can I also include unpaid late fee and interest from previous periods' late rent payments in the notice?

In eviction court if you do not correctly fill out your notice to pay rent, your tenant's attorney can easily get the case thrown out.

I can write down paragraphs of information about California eviction law and notices, but you need to educate yourself and have your eviction attorney prepare your notice. You can NOT include any LATE FEE'S if you plan to use this notice in an eviction procedure.

Amy have you heard the term "right from the horse's mouth"?

Commercial is different from residential. I forgot CA law on this, but in general you can just start eviction, and in some cases I believe you can just tap the till, though that may be a contractual thing.

Also in some places you can just lock the doors with all their products and property inside. I would consult a local commercial property lawyer on this. It is far different than residential.

Another vote to hire a professional competent commercial eviction lawyer, it will be money worth spending in your situation.