Many journals accept simultaneous submissions, which is when you send the same work to several journals. (Although not all do. Always check the writers’ guidelines.) The vast majority of journals are looking for first publication rights, which means they want to be the first to publish the work. As a result, it’s vital that you withdraw your submissions from other journals once it is accepted for publication. Make sure you keep a list of where your work is under consideration so you know which journals to contact should you need to.
Journals that use online submission programs often have an option to withdraw, making it just a simple click. For those journals that don’t have such programs, you can withdraw your submission via email if the editors are open to such correspondence. Otherwise, send a note in the mail. Simply state you are withdrawing the submission because it is being published elsewhere. Note the title of the work and the approximate date of submission, too. It’s not uncommon to follow up with another submission.
This practice keeps editors updated on the status of your work. A great deal of time and energy goes into considering submissions, so letting them know the work isn’t available will allow them to give that attention to other submissions—including your next one.