Select the text you want to strikethrough
Click the Format Text tab
Click the Strikethrough button in the Font group
On Windows, use Ctrl+D to open the Font dialog, then check Strikethrough
On Mac, use Command+Shift+X
In Outlook on the web, select the text, then click the More formatting options button and choose Strikethrough
To remove strikethrough, select the text again and click Strikethrough or use the same shortcut