The disappearing leading zero
Excel treats anything that looks like a number as a number, and numbers do not have leading zeros. Type 00421 and you get 421, with no warning, because as a quantity those are the same thing.
As a code they are not the same thing at all. Product codes, phone numbers, sort codes and postcodes are labels that happen to use digits, and the zeros carry meaning.
The fix is to tell Excel it is text. Typing an apostrophe first, '00421, stores the value as text and the apostrophe is not part of it. The cell contents become left-aligned, which is the visual confirmation it worked.
The codes in B3 and B4 have lost their leading zeros. Retype both so they read 00421 and 00533, with the zeros intact.
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