Submission is automatic, it isn't instant (unless you create a cc_config.xml file for BOINC). Depending on your settings and the length of WUs you choose to work on, BOINC will automatically submit results at different times. BOINC will definitely submit your work before the WU deadline approaches however.
If you want instant reporting, you can read up on cc_config.xml here: http://boinc.berkeley.edu/wiki/Client_configuration.
The option you would want:
If 1, each job will be reported to the project server as soon as it's finished, with an inbuild 60 second delay from completion of result upload. (normally it's deferred for up to a day, so that several jobs can be reported in one request). Using this option increases the load on project servers, and should generally be avoided. It's intended to be used on computer whose disks are reformatted every day.