If your text is always 3 characters, then one way:

=LEFT(A1,3) & "-" & MID(A1,4,255)

where 255 is just a big number to ensure all the digits are captured.

In article .com,
"Accounts jobs" wrote:

If anyone can help me in this I would be very greatful

We receive a list of codes like "TND4567". We manually put the dash
between the text and numbers. is there any way of doing it through a
formula in excel.