Base rent is the fixed minimum rent owed under a lease, before escalations, percentage rent, or expense reimbursements.
Base rent is the starting point for valuing an NNN property, since it is the amount that flows to the landlord once the tenant pays taxes, insurance, and maintenance separately. Cap rate calculations rely on it, so the buyer should confirm that the rent in the offering materials matches the lease and the tenant's actual payments. Base rent usually steps up on a schedule, and some leases add percentage rent on top, so always look at the full rent schedule rather than just the current monthly figure.