Out of the box this feature doesn't existing. Many people use some JavaScript attached to the OnChange event of the field to do the formatting.
Here is an example that could be used for any phone/fax field - the code would need to be placed into a JavaScript web resource file and the PhoneFieldChange method attached to any phone number field's OnChange event (remembering the check the box to pass the execution context). The downside to this in conjunction with the new "process" user experience forms is that JavaScript is not supported. There you would need to create some .NET code in the form of a plugin or custom workflow assembly to do the formatting on the server side.
Sample JavaScript:
function PhoneFieldChange(context) { var value = context.getEventSource().getValue(); if (typeof(value) != "undefined" && value != null) { value = Avastone.FormatPhone(value); } context.getEventSource().setValue(value); } function FormatPhone(inputValue) { var scrubbed = inputValue.toString().replace(/[^0-9]/g, ""); if (scrubbed.length < 7) { return inputValue; } var sevenDigitFormat = /^\(?([0-9]{3})[-. ]?([0-9]{4})$/; var tenDigitFormat = /^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$/; var extDigitFormat = /^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})?([0-9]*)$/; if (tenDigitFormat.test(scrubbed)) { return scrubbed.replace(tenDigitFormat, "($1) $2-$3"); } else if (sevenDigitFormat.test(scrubbed)) { return scrubbed.replace(sevenDigitFormat, "$1-$2"); } else if (extDigitFormat.test(scrubbed)) { return scrubbed.replace(extDigitFormat, "($1) $2-$3 x$4"); } return inputValue; }