In a formula column, the MULTIPLY() function allows you to multiply the content of several columns.
MULTIPLY(Amount before tax, VAT rate)
I have multiplied the content of my Amount before tax column with the content of my VAT rate column to get the amount of my VAT in the column of the same name.
MULTIPLY(Amount before tax, 0.2)
I have directly multiplied the content of my column Amount before tax with 0.2. This formula will be valid for the whole column.
This can be useful if you use a fixed rate, it allows you to delete the VAT rate column from my example 1.