9.25 'so' and 'not' after 'if'

'So' is used to substitute for a clause after 'if', when the action or situation you are talking about has already been mentioned.

• Will that be enough? If so, do not ask for more.

'Not' is used to substitute for a negative clause, to imply the opposite situation to the one already mentioned.

• You will probably have one of the two documents mentioned below. If not, you will have to buy one.