Notice of Rent Increase

Landlords may increase the rent for any number of reasons, as long as it is not contractually or legally forbidden. Some of the most common reasons include higher property taxes, higher cost of living, rising property value, higher landlord insurance premiums, etc. On the other hand, a landlord cannot raise the rent if it's ruled out in the lease agreement or outlawed by the local rent control law.

The landlord may decide to deliver the notice in person, via email, by mail, or arrange to have someone or a company deliver it to the tenant's door. The original lease agreement may specify how future documents are to be forwarded to be valid. Consult the lease before sending your Notice of Rent Increase.

The most obvious consequence is that a landlord would be unable to enforce the rent increase without a Notice of Rent Increase. A verbal agreement does not legally replace a physical notice.

If not otherwise prohibited by the lease agreement, a landlord can send a Notice of Rent Increase at any time. However, it is standard practice to inform a tenant at least 30 days in advance. Depending on your state and jurisdiction, there may be a mandatory notice period of at least 15 days.

There is no limit except if prohibited by law. In general, landlords can raise rents by 1-2% every couple of years without raising eyebrows. For difficult tenants, such as those who have a history of inflicting property damage, it is not unheard of for landlords to charge 3-4% or more, perhaps to recoup losses or as insurance against future damage. 
To avoid pricing your property out of the market, check rental rates for comparable properties to yours in the area.

This type of notice is not designed for use regarding fixed-term leases. Without a mutual agreement, the landlord cannot raise the tenant’s rent in the middle of the fixed term.

However, since fixed-term leases don’t automatically renew, an increase in the rent will be an aspect included in the renegotiation of the lease.

Generally, you will deliver a notice of rent increase either by mail - first class, registered, or certified - hand delivery, or door affixation. You should still check your state’s tenant laws to ensure compliance.