A substitution passes your entry to a different person so they can race instead of you. If instead you want to move your own entry to another event or distance, see the article on transfers.
Not every event allows substitutions. Some organisers offer a credit exchange instead, which you can use another time.
How to substitute someone onto your entry
Make sure you are logged in to Race Space. If you are not, go to www.race-space.com, open the main menu and select Register/Login.
Select My Entries. You will see a list of every entry you have bought.
Move to the far right of the row and select Entry Actions, then Substitution.
Follow the steps to complete the substitution.
There may be a charge. You can either pay it yourself or pass it on to the person taking your place.
If you are not sure yet whether a substitution is the right option, start with the article on what to do if you cannot attend.