Can you use bicarbonate of soda instead of baking powder?

Yes they are the same. In Australia you tend to say bicarb of soda but in America you tend to say baking powder (these terms are used elsewhere but to keep it simple I'll just put these two). however there is also baking powder this is a different substance and cannot (or should not) be a substitute (or substituted) for bicarb of soda. hope this helped!