The most common types of dependencies in projects are^ Finish-to-start (FS) – when the successor task cannot start until the predecessor task has finished. Start-to-start (SS) – when the successor task cannot start until the predecessor task has started. Finish-to-finish (FF) – when the successor task cannot finish until the predecessor task has finished. Start-to-finish (SF) – when the successor task cannot finish until the predecessor task has started.