The Act Number indicates what Act you're in. It can indicate the beginning of a new act or the continuation of the current Act. Act numbers are usually only used in Sitcom or Play scripts.
Act Numbers look like this:ACT IIACT THREEACT 4
The numbering style you use depends on both your taste and/or the style in use by the show for which you're writing. In other words, if you're writing a "Murphy Brown" script, use the numbering style that they use (more about this in Give 'em what they want
There are a couple of other acts that don't have numbers but, instead, have names. If you have these, there will be no more than one before Act 1 that might be called TEASER, COLD OPENING, or PROLOGUE. There might also be one following the final act called EPILOGUE or TAG. In a sitcom, a teaser, or cold opening takes place before the first commercial break and the tag takes place after the last commercial. Both of these parts of the script don't have anything specifically to do with the story and could be removed from the show (which is often what happens when a show gets syndicated so that the syndicators can squeeze in more commercials). The prologue and epilogue occupy the same place at the beginning and end of the show, but are an integral part of the story. See what the show's standard for using these are before you decide you need to use them.
Some shows only want you to put the Act Number on the first page of a new act. Others want you to put it there and on the first page of each new scene within the act (see Scene Numbers). Typically, there is only one scene in a Prologue, Teaser, Cold Opening, Tag, or Epilogue.
Similarly, some shows want you to indicate the ending of an Act by typing something like:END OF ACT 5END OF TEASER
That would be the last line of the page, then, the top of the next page would be the next act.
Act Numbers are uppercase. Center them horizontally on the page. For a new act, put the Act Number 2" from the top of the page. Start each new Act on a new page.
The End Of Act indicator is also centered horizontally and uppercase. Put two blank lines between it and the last line at the end of the act.
If a show uses letters instead of numbers for each act, it typically will not use certain letters. Most commonly, shows will not use the letters "i" or "o" because the capital versions of those letters look too much like the numbers one and zero.
When you want to start a new act, make sure the cursor on a blank Action element and type "act" and press <Enter>.
Scriptware will start a new page for you, put the Act Number, centered, in the proper place on the screen. add the correct number in the correct format and, if you want, automatically add the End Of Act indicator on the previous page!