I have this formula

=IF(LEN(TA!D2)6,--RIGHT(TA!D2,6),TA!D2)

and it will take the last 6 numbers of a receipt from work book TA, line D2
and leave only the last six digits.

That is it will take 1234654318983

and leave 318983

It will only work with numbers. I have some receipts that have letters as
the last characters in the sequence.

How can I get the formula to work with letters as well as numbers?