In a column of type formula, the SUM () function is used to add the contents of several columns to each other.
SUM (Column1, Column2, Column3, Column4, Column5)
SUM (Amount HT, VAT)
I added the column Amount HT with the VAT column.
SUM (Amount without VAT, VAT, 12.90)
In addition to example 1, I added 12.90 which correspond, for example, to the unpublished costs of Colissimo.
NB: In the same logic, I can subtract a sum, simply by adding a negative number:
SUM (Amount without VAT, VAT, -10)