In Austria, a contract is concluded by offer and acceptance. The offer must be specific and serious in terms of content. The acceptance must relate exactly to the offer made, unless there is a "counteroffer", which, in turn, must be accepted unchanged. 

A contract is only concluded when the contracting parties agree on all the essential contractual content: usually the subject matter of the service and the remuneration (the consideration). 

Info: In every contract, you simultaneously take on the role of debtor and creditor. Debtors owe a service. Creditors may demand this performance. You are therefore the debtor of your own performance and at the same time the creditor of the consideration of your contractual partner.

If you and your contractual partners agree on performance and consideration, the contract can already be concluded. You can—but do not have to—regulate many other contractual conditions (e.g. confidentiality obligations, contractual penalties).

If there are no specific provisions in your contract, the general statutory provisions apply. In Austria, these are primarily the provisions of the General Civil Code (ABGB). Labour laws, such as the Working Hours Act and the Holiday Act, apply to employment contracts. If artists conclude a contract for the transfer of rights of use to their works of art, the provisions of the Copyright Act may apply.

Example: You are a photographer, and someone hires you to take photos for a fashion catalogue. The catalogue is to be published in print and uploaded to the company's website. You have agreed that the company may use the photos, but have not agreed on the exact details as to how they may use these photos. The regulation in the Copyright Act applies, according to which you only grant your contractual partner as many rights as are necessary to achieve the purpose of the contract. This means that the company may reproduce and publish the photos in the fashion catalogue and make them publicly available on the website.