I salary sacrificed some profit - can this offset the capital gains tax?

Q.

Last year I earned $54,000 but sold some shares bringing my total earnings to $73,000 attracting capital gains tax of $4,300. I salary sacrificed $3,500 - can this offset the capital gains tax?

CGT is calculated by adding the net gain to your taxable income. Therefore, salary sacrificed contributions which reduce that taxable income may help reduce CGT. However, in your case you are remaining in the 30% bracket, so the salary sacrifice contribution is of no additional benefit to you.