=IF(LEFT(B132,1)="0","SSR"&B132,IF(LEFT(B132,1)<>"0","SSR00000"&B132,IF(B132
<> "",RIGHT(B132,LEN(B132)-SEARCH("SSR", B132)+1))))


The <> "0" not equal to condition will return everthing that is not in your first expression ="0" hence fulfilling that condition so the third condition will never be reached!

=IF(isnumber(A17),"XXX"&text(A17,"0000000000"),IF( A17 <> "",RIGHT(A17,
> LEN(A17)-SEARCH("XXX", A17)+1),""))

Would eliminate the false and deal with the numbers if they were added as numbers

If however it is inconsistent and some are numbers and some are text the 2 expressions would have to be combined

Try something like
=IF(isnumber(A17),"XXX"&text(A17,"0000000000"),IF(LEFT(A17,1)="0","XXX"&A17,IF(A17 <> "",RIGHT(A17, LEN(A17)-SEARCH("XXX", A17)+1),"")))

If it is just a number then "xxx" and a ten digit number with leading zeros
Else if it is text starting with a 0 then 'xxx' and the text
Else if it the normal text string trim it to the bit starting XXX

if statements are a pain, especially just before a weekend, especially when they are nested they can become quite messy and the order of the conditions in crucial as it is actually else if

Anyway I think the above should work

If not please let me know


Regards

Dav