The Tax-Free Childcare scheme is being rolled out by the government during 2017 and will eventually replace the current Childcare Vouchers Scheme
To help with the transition between the two schemes, the current childcare voucher scheme will remain open to new joiners until April 2018, giving parents more time to sign up but after this date it will no longer be available to new entrants.
USEFUL LINKS:
https://www.gov.uk/childcare-vouchers-better-off-calculator
(this page last updated Aug 2017)