Why is to_char left padding with spaces? When ever I use 099 indicating 3 digits 0-padded, I'm getting spaces on the left side.

SELECT '&gt;' || to_char(1, '099') || '&lt;';
 ?column? 
----------
 &gt; 001&lt;
(1 row)


Why is to_char left padding here? Why are there leading spaces?
You can see that in a simpler test case here

SELECT '&gt;' || to_char(1, '0') || '&lt;';
 ?column? 
----------
 &gt; 1&lt;
(1 row)


This is because, as @Abelisto said, the space is reserved for the sign glyph,

SELECT '&gt;' || to_char(-1, '0') || '&lt;';
 ?column? 
----------
 &gt;-1&lt;
(1 row)


You can suppress the sign using FM, from the docs

Modifier Description Example
FM       prefix      fill mode (suppress leading zeroes and padding blanks) FM9999


So what you want is

SELECT '&gt;' || to_char(1, 'FM099') || '&lt;';


The zeros aren't suppressed when you demand them with FM0