The Costume Designer is responsible for creating an appropriate look for the costumes worn by the cast, both from the viewpoint of functionality (e.g. are there lines in the show that refer to specific aspects of the costume; will the costumes need to hide radio microphones or other special effects; are they suitable for any quick costume changes), and from the artistic appearance of the costumes (from the correct time period). This may involve making the costumes from scratch, altering existing costumes, or arranging costume hire from a third-party firm. The Costume Designer will also need to arrange suitable transport for getting the costumes to the theatre at the start of the run, and removing them after the last performance.
Some directors will have a very strong view about the overall design, whereas others will give their designers a greater input into creating the look of the show.
For best results, the Costume Designer should work with the other designers to ensure the costume design is consistent with the overall design ideas. A production will look a lot better if each designer is following a consistent thread and taking into account of the look and atmosphere being created by the other designers.
The Costume Designer is almost always responsible for making and/or sourcing hire costumes based on the design, and sometimes they also take on the role of looking after the costumes during the run of the show. You should confirm with the production team whether you are happy to be present for the full run of the show, so that Wardrobe Assistants can be found to do this job if necessary. You should also discuss whether there are any quick costume changes that will require additional Wardrobe Assistants to be found to help actors with these changes.