Try this, if it shows up as " ", then you know it's a format issue

=IF(ISERROR(VLOOKUP(B10,ProductLookup,2,FALSE)),"
",VLOOKUP(B10,ProductLookup,2,FALSE))

Try copying the lookup numbers and pasting them as values then seeing if
their is a little question mark or some little box that you can click and
convert them from text to numbers.

"NANGO" wrote:

I have a spreadsheet which uses a VLOOKUP of approximately 30,000 item
numbers on a different tab called Product Lookup, to provide description,
price and 4 other pieces of information.

For some reason, some of my item numbers cannot be found even though they
are on the Product Lookup and all my item numbers are sorted in ascending
order.

The only way I can get the information I'm looking for to show up is if
manually go to the Product Lookup tab and copy the Item number I want and
paste it in the other tab.

Here is the the code I'm using

=IF(B10="","",VLOOKUP(B10,ProductLookup,2,FALSE))

Any ideas on why this might be happening?