'have now decided' is correct and usable in written English.
You can use it when you need to refer to a decision that has been made recently. For example, "We have now decided to proceed with the project as planned."
Police have now decided there are no grounds for action.
They have now decided to dissolve the partnership.
Del Webb executives have now decided to allow outside contractors here.
And it is this achievement that the Taliban and bin Laden have now decided to challenge.
"We have now decided it is best to approach the government.
Inter have now decided to "draw a line" under the incident.
But surgeons have now decided instead to fit the metal plate.
The odd thing is that Auden's poems are often saying the reverse of what we have now decided to hear.
We did talk to Lagos for about 18 months and we have now decided not to continue these discussions".
On Wednesday the OFT reported that eight of the top lenders have now decided to stop offering payday loans.
Wasps have now decided to dump the girl they came with and dance with someone else from the Midlands.
