You should always boil fresh tap water when preparing a feed, but then let it cool for up to 30 minutes so it reaches around 70°C before measuring into your baby bottle and adding the correct number of scoops of formula. Using boiled water of at least 70°C to make up the feed will reduce any risk of your baby becoming unwell with infections like sickness or diarrhea. This is because any harmful bacteria present will be killed at this temperature.
Remember to always check the temperature of a feed before giving to baby - it should be body temperature - you can check this on the back of your wrist.