Dynamic SumIF Formulas That Reference Changing Codes

I have a list of codes from which I'm trying to extract all unique entries.

For example, col A has 001, 001, 002, 003, 003, 003, 004, ...

I'm trying to create a report template with formulas that reference col A and return a single unique entry for each code so that the new column has only 001, 002, 003, 004.

Essentially, the codes reference customers. A customer can have multiple purchases -- but I'm trying to create a report in which I can utilize SumIf formulas to Sum the purchases for each customer and represent those purchases on a single line per customer code.

The catch is that the purchases change monthly (i.e., next month the purchases may be 001, 002, 002, 002, 004) so my report template needs to have the flexibility to adapt without me rewriting the SumIf formulas and return SumIf results for only customers 001, 002, 004. Whereas in the prior month, the report returned SumIf results for customers 001, 002, 003, 004.