The phrase 'when it has finished' is correct and usable in written English.
You can use it when referring to an action that has not completed yet but will do so at some point in the future. For example, "I will call you when it has finished."
Remove the thermometer slowly and gently when it has finished taking its reading.
However, Clematis montana is prunable - just take the shears to it when it has finished flowering.
The letter the dreidel shows when it has finished spinning determines whether players win or loose the coins.
The shuttle is due to be retired in 2010 when it has finished construction of the International Space Station.
Project managers can use a number of applications offering a wide range of functions in the areas of project planning, monitoring and continuous evaluation of project implementation, and final evaluation when it has finished.
When it has finished, your laptop will reboot and everything should be exactly as it was before, except on a new drive.
We went to the cinema that was part of the same complex, watched a movie and when it had finished hid in the ballroom itself all day.
That dissipates as soon as the monster makes his intentions known, declaring that it will tell Conor three stories and that when it has finishes recounting each one, the boy must describe his worst nightmare.
"I'll talk about it when I've finished my career in a lot more detail but I copped a lot of stick and I had to have the self-drive and self-confidence to achieve what I wanted to achieve".
Williams was ahead by 23 of nearly 290,000 votes cast when the election board said it had finished its work.
When I had finished it, I showed it to Huw Wheldon at the BBC.
