Standard Clauses for use in drafting a lease for a multi-tenant office building in New York. In these Standard Clauses, the tenant pays its proportionate share of the increases in real estate taxes and operating expenses above those expenses incurred in a base year. A lease with this type of escalation payment arrangement is sometimes called a modified gross lease or a base year model gross lease. These Standard Clauses have integrated notes with important explanations and drafting and negotiating tips for escalations in an office lease.