I’m currently rewriting my SP “Revenge”.     The SP is loaded with flashbacks.   Do they work?  Some of them do and some of them don’t … I’m working on that right now.  But what I’ve found is that there are several ways to show the flashback in a screenplay.

There are two things to consider, the first being … how long is the flashback? 

Is the flashback shown in one scene or does the flashback constitute more than one scene? 

If the flashback is just one scene, alert the reader to the flashback in the slug-line.  Some ways you can show this: 

FLASHBACK – INT. or EXT.   LOCATION  – DAY or NIGHT

INT. or EXT.  LOCATION -  DAY or NIGHT (FLASHBACK)

INT. or EXT.  LOCATION  – DAY or NIGHT – FLASHBACK

The first slug-line after the flashback should indicate that we are returning to present day.  This can be done in a couple of ways:

INT. or EXT.   LOCATION – DAY or NIGHT – PRESENT DAY

INT. or EXT.  LOCATION – DAY or NIGHT (PRESENT DAY)

If there are several scenes in a flashback, each SLUG-LINE should have “FLASHBACK SEQUENCE” noted in it.

INT. or EXT.  LOCATION – DAY or NIGHT (FLASHBACK SEQUENCE)

INT. or EXT. LOCATION – DAY or NIGHT – FLASHBACK SEQUENCE

And then, like the single scene flashback, make sure you note in a slugline when  the reader returns to present day.

I have seen the flashback presented in other ways, too.    One way is to use a  HEADING to note the beginning and ending of a flashback.

Example:  FLASHBACK SEQUENCE … END OF FLASHBACK SEQUENCE

or

Example:  FLASHBACK BEGINS …  FLASHBACK ENDS.

There are many ways to show a FLASHBACK.  I would suggest that you choose the one you like best, but be consistent throughout your project.

And remember that the flashback is written in PRESENT TENSE, just like any other scene!