Childcare vouchers are currently being phased out by the government and replaced by a new government offer of “tax-free childcare”. They are only available to employees who had already joined the scheme and had their wages adjusted on or before 4 October 2018. You can’t use both childcare vouchers and tax-free childcare.
Childcare vouchers are offered to existing employees either on top or instead of a portion of their salary (known as ‘salary sacrifice’). Vouchers can affect your eligibility for Universal Credit.
These vouchers are free of tax and National Insurance Contributions up to a limit linked to the amount of income tax you pay and can be used to pay for registered childcare.
Where vouchers are provided through salary sacrifice, your employer does not have to carry on providing them during your maternity leave (unless your employment contract gives you this right).
You can find more information on the website of the charity Working Families.