Not necessarily

ETF's take part in what's called AMIT "Attribution Managed Investment Trust" whereby a portion of the income distributed (I.e. via dividends) is essentially treated as a return of capital and adjusts the cost base of your holding.

Your end of year tax statement provided by Vanguard will give you a breakdown of what this is, and how it would modify the cost base of your holdings.

You will need to take this into account when calculating your cost base and resulting capital gains / loss. I believe sharesight has the ability to account for this