lisäsopimukseen

Lisäsopimus, English‑language term “supplementary agreement”, is a contractual document that modifies, extends, or clarifies terms of an existing agreement. It is used when parties decide to change a specific provision or add new obligations without drafting a completely new contract. The original agreement remains valid, while the lisäsopimus applies to the changes specified. It can be realized by written or, in certain jurisdictions, by oral modifications, provided the parties consent and the new terms are express or implied.

In Finnish contract law, a lisäsopimukseen can be prosecuted as a separate document or incorporated in a memorandum that references the main contract. The Helsingfors case clarified that a supplementary agreement is enforceable when the parties mutually agree on the new terms and the changes are adequately documented. The law requires that a lisäsopimus be clear on what provisions it alters, adds, or repeals, to avoid ambiguity and to preserve the original contract’s core terms.

Typical applications include adjustment of delivery schedules, price changes, or amendment of technical specifications. In employment law a lisäsopimus can modify working hours or benefits while keeping the core employment agreement intact. In real estate sales, a lisäsopimus might address additional fixtures or alterations to a property that were not considered in the original sale deed.

To be legally valid, a lisäsopimukseen must respect general contract principles such as consent, capacity, and legality. It is strongly advised to draft the document in clear, unambiguous language, indicate the parties’ identifiers, and state the date of signing. The signed agreement must be stored alongside the original contract to preserve the documented evolution of the parties’ obligations.