Tax code changed by HMRC but employer yet to update

My tax code was changed by HMRC over a week ago but my employer indicated that they are yet to receive notification from HMRC. How long does it take for HMRC to inform employer about tax code change. Any advice on best way to follow up?

Hi,

The tax code would be sent online to the employer so normally received 3 to 5 working days to their online account.

If you ask your employer to check their online account the code should be there. 

Thank you.