Sending the same piece of writing to multiple literary magazines or contests at the same time instead of waiting for each one to respond.
A simultaneous submission means you send the same story, poem, or essay to more than one publication at once. This is standard practice in the literary world because response times from magazines can range from a few weeks to over six months. Without sim subs, a single short story could take years to find a home. Most literary magazines explicitly allow simultaneous submissions, but they require you to notify them immediately if your piece is accepted elsewhere so they can remove it from consideration.
If you are serious about getting published, simultaneous submissions are not optional - they are how the system works. A magazine might take four months to respond. If you submit to one place at a time, you could spend two years on a single story before it finds a home or you run out of markets. Sim subs let you play the numbers game while your writing is still fresh and you still care about placing it.
The moment you get an acceptance, immediately log into every other platform where that piece is pending and withdraw it. This is a courtesy that protects your reputation. Editors talk to each other, and failing to withdraw burns bridges fast.
Use a spreadsheet or a tool like Submittable, Duotrope, or The Submission Grinder to track every submission - where you sent it, when, and the current status. Without a system, you will lose track within a month.
A small number of publications do not allow simultaneous submissions. Always read the submission guidelines fully before sending. If a magazine says no sim subs, either submit exclusively to them or skip them until you have a piece you are willing to wait on.
While the piece itself stays the same, your cover letter should be personalized for each magazine. Mention why your piece fits that specific publication. Editors can tell when they are getting a generic cover letter.
Take a finished piece of writing and identify five publications that accept simultaneous submissions and seem like a good fit. Create a simple tracking spreadsheet with columns for publication name, date submitted, response time listed on their website, and status. Submit to all five within the same week and keep the spreadsheet updated. This exercise is as much about building a submission system as it is about getting published.