A format code has four parts separated by semicolons: positive; negative; zero; text. Most people never see past the first. Once you can write them, the finance conventions Excel has no button for become one-liners — #,##0;(#,##0) puts negatives in brackets the way an accountant expects, #,##0, shows a figure in thousands WITHOUT dividing anything (the trailing comma is the whole trick, and the underlying number is untouched so nothing downstream breaks), and ;;; hides a cell's contents while leaving the value there for formulas to use.

1. 1Ctrl + 1, then the **Custom** category at the bottom of the list.
2. 2Type the code in the Type box. The sample above it updates as you type.
3. 3Four parts, semicolon-separated: positive; negative; zero; text. Omit the later ones and they fall back.

Press the shortcut to play it on a sample sheet.

• Brackets and red for negatives, the way a board pack expects.
• Show a schedule in thousands without touching the underlying numbers.
• Hide a working column with ;;; instead of hiding the column itself.