When installing Linux Mint 18.1 with GRUB UEFI enabled it will fail with the error
“grub-efi-amd64-signed failed to install into /target…”

So when you get to this point don’t close anything just open a terminal and type the below commands to install GRUB manually to the EFI partition.

sudo mount /dev/sda3 /mnt #sda3 is the root partition
sudo mount /dev/sda1 /mnt/boot/efi #sda1 is the efi partition
for i in /dev /dev/pts /proc /sys; do sudo mount -B $i /mnt$i; done
sudo cp /etc/resolv.conf /mnt/etc/ #makes the network available after chrooting
modprobe efivars # make sure this is loaded
sudo chroot /mnt
apt-get install --reinstall grub-efi-amd64-signed #If apt-get fails remove the --reinstall option
update-grub

Now press Ctrl+D to exit chroot enviroment and unmount everything before rebooting.

for i in /sys /proc /dev/pts /dev; do sudo umount /mnt$i; done
sudo umount /mnt/boot/efi #please do this. Corrupted efi partitions are not nice
sudo umount /mnt

Now finish the installation and reboot into Linux Mint 18.1

Source: superuser.com