Change lease at the end of lease term

If someone's lease is ending at the end of this month am I able to change something in it when it does end? It will automatically go to Month to Month status as of September 1st. What I am wanting to change is adding a month to month fee, for some reason this was not put into the lease when she signed it to being with. If I am able to change it how many days notice do I need to give her?

Do you use a NAA lease or a different lease? If you use the NAA lease, if you look in the first six pages of the lease and go to paragraph 15 it states:

"No rent increases or Lease Contract changes are allowed before the initial lease contract term ends, except for changes allowed by any special provisions in paragraph 10, by any signed written addendum or amendment signed by you and us, or by reasonable changes of apartment rules allowed under paragraph 18. If, at least 5 days before the advance notice deadline referred to in paragraph 3, we give you written notice of rent increases or lease contract changes effective when the lease contract term or renewal period ends, the lease contract will automatically continue month to month with the increased rent or lease contract changes. The new modified lease contract will begin on the date stated in the notice (without necessity of your signature)unless you give us written move-out notice under paragraph 37."

I hope this helps. My last property when had a MTM addendum that they signed when they signed the original lease. We later ended up changing the amount we charged, but if they signed the old addendum then they were only charged that price instead of the new price. At my current property, we do not have that addendum. When their lease is up and they do not renew then they are charged market rate plus $100.00 MTM fee.