The UK government has proposed big changes to the childcare voucher scheme which will not take affect for at least two years from now (2013). However, one of the biggest changes will be that at first the new scheme will only apply to children under five, with plans to eventually roll it out for older children. This means if your employer does provide a voucher scheme it is a good idea to get on it before these changes come in, as you will not be eligible for help with out of school care costs under the new scheme.
Employers can provide childcare vouchers and they pay reduced national insurance contributions on the amount they provide. Most OSC services will accept childcare vouchers.
The current scheme is fully explained in this government brochure
As noted under Childcare Tax Credits you might lose out if you accept employer vouchers if you are borderline in terms of being able to get Childcare Tax Credits. You can use this calculator to help work out what is best for you.
If you are receiving tax credits and want to know whether you would be better off with childcare vouchers, please go to the online calculator at www.hmrc.gov.uk/calcs/ccin.htm