Here is an easy formatting guide to setting up flashbacks in your screenplay.
There are headings for almost all types of film and scene devices in screenplay writing. This is not just true for master and secondary scenes, but also alternative constructs that do not adhere to the same linear progression that is in the main storyline of your film. One of these that are often used in contemporary film and television is the flashback. This is done so that you can see preceding events in a fashion that is clear instead of just created in the audience's mind through allusion.
For a flashback you will actually do an altered version of the master or secondary heading. Often times the choice to use one or the other depends on what situation it is in. When it occurs mid master scene, such as when a character begins actively telling a story from the past in a scene. In this situation you can just approach it as a specially labeled secondary heading.
Example: FLASHBACK – TOM COOKING DINNER WITH HIS MOM
If this is the case then you are going to want to adhere to the limitations of a secondary scene posting, such as keeping this short.
If you want the flashback to hold more weight and be viewed on par with other scenes then you may want to present it as a master scene. To do this you simply alter the format commonly used in master headings.
Example: EXT. SOUTHLAND BEACH PARK – DUSK – FLASHBACK
There is really no concrete way that you have to break up words in the flashback master heading. You can choose to use hyphens, parenthesis, or even just open spaces. As long as you maintain the word order and proper information then you will be fine.
Close Me Out
Once the flashback is done, especially if it is occurring in the middle of a master scene, then you need to indicate that you are returning to the regular temporal world. Again, there is no standard way of phrasing it. RETURNING TO PROPER TIME is often a good way to indicate that you are now in the standard story flow of the screenplay. Make sure to capitalize all parts of this, including both the heading and the closing line.