The following information only applies to employees who work for the National Health Service.
In a Career Average Revalued Earnings (CARE) scheme, like the 2015 NHS Pension Scheme, pension benefits are built up on a year by year basis based on your actual pensionable earnings in each year. Therefore entering into any salary sacrifice arrangement (e.g. Childcare Vouchers, Lease Car Schemes etc) that reduces your gross pensionable earnings will have a negative effect on the amount of pension you are able to build up in that year. The overall effect from participating in any salary sacrifice scheme would be to reduce the amount of final benefits you earn.
If you are unsure as to how any salary sacrifice arrangement you are currently a member of, or wish to join, may affect you then please talk to your employer.