einen Vertrag kündigen

You usually use it with the verb kündigen at the end. For example, Ich möchte meinen Vertrag kündigen. If you already did it, say Ich habe gekündigt. You can also specify what kind of contract it is. Just swap Vertrag for Mietvertrag (lease) or Arbeitsvertrag (job contract). It is a strong, active verb. It requires a clear intention and usually a signature.

Use this when dealing with companies or landlords. Use it when you find a better phone deal. Use it when you are moving to a new city. It is perfect for professional settings too. If you are quitting your job, this is the phrase. It shows you know the formal process. Even if you're just telling a friend, it works. 'I finally canceled that expensive gym!' feels great to say.

Do not use this for personal relationships. If you break up with a partner, don't say you're 'terminating the contract.' That sounds like a robot ending a romance! Use Schluss machen instead. Also, don't use it for small things. You don't 'kündigen' a dinner reservation. You just 'absagen' (cancel) that. Save kündigen for things involving paperwork and signatures.

Germany is famous for its 'Vertragskultur' (contract culture). People love the security of a long-term agreement. However, this means you must watch the Kündigungsfrist (notice period). Often, you must cancel three months before the contract ends. If you miss the window, it might auto-renew. Germans are very disciplined about sending these letters. It is a rite of passage for any expat. Learning to kündigen is a sign of true integration.

You will often hear fristgerecht kündigen. This means canceling within the legal time limit. Then there is fristlos kündigen. This is the 'emergency' version for immediate termination. You might also hear die Kündigung einreichen. This means 'to submit the resignation.' Each variation carries a slightly different weight. Always double-check your dates before you say it!