is there a restriction on the maximum % of salary that can be contributed to NEST by either the employee or the employer?
I don’t see that the restriction would be any different to the annual allowance for any pension scheme. Why anyone would want to put £40k in a scheme such as Nest is a different matter.
There is a higher limit of £40K pa (there are other refinements that mean you could pay higher than this if the full entitlement has not been taken in the last 3 years)
As such there is no lower limit......... but the employer cannot pay an employee less than the minimum wage without failing foul of the minimum wage legislation - so no putting all of an employees salary in!