Reimbursement from Tenants for utilities

[Dave S.]

So here is the scenario....Utility bill comes to my address (these specific utilities are in my name), I pay for them so that they are on time with no late fee. The next month the tenants reimburses me. Wouldn't the reimbursement from the tenant be considered "income" and I would have to pay taxes on that? If not how would i classify these transactions for tax purposes?