Elapsed days invoice aging

Is that the whole formula? The formula looks correct other than the comma on the end.

What issues are you having with it? If there is more to it as the comma suggests post that part because this looks right to me.

Try this:

ToDays( Today()-[Date Invoice Sent to Client] )

Notes:
- You had an extra comma at the end
- Since [Date Invoice Sent to Client] is already a Date field, you don't need to convert it with the "ToDate" function

Hope this helps!

Formula looks fine to me. Works in my test app. Pardon the question - you've reproduced it here with an errant trailing comma - is that character in your formula?

EDIT to clarify: this formula works if [Date Invoice Sent To Client] is a date/time or text field. It will NOT work if that field is a simple date field. However, if that were the issue you'd be seeing this error:
"Formula error -- Bad or missing arguments in function call"
rather than 
"Formula syntax error -- There are extra characters beyond the end of the formula"

Thanks to @Xavier Fan for narrowing that down

Alex.... that worked just fine.  Thank you!

Dirk