Lease renewal. Cleaning of a Rinnai heater

[Joe C.]

I have a tenant who's initial 1 year lease is about to end. She was offered an extension for one year which she agreed to. I require tenants to pay for a yearly cleaning of the Rinnai heater but in this case forgot to mention it when I offered the extension. Should I mention it after the fact or eat the expense. Thanks in advance for your answers.