Hi TheMrs,
The NIC you are referring to which is payable on the Form P11D is employer Class 1A NIC at 13.8%. This is payable to HMRC by 22 July following the end of the tax year if paying electronically.
The 22 April deadline you are referring to is for paying the PAYE/NIC for the 2016/17 tax year to HMRC. This is completely separate to the Class 1A NIC payment mentioned above.
In terms of next steps therefore you need to do the following. Go to this link
https://www.gov.uk/pay-class-1a-national-insurance and follow the instructions to make payment of the Class 1A NIC and ensure you use the Class 1A NIC payment reference to enable HMRC to allocate this correctly.
The £701 you have already paid will be allocated by HMRC to the PAYE/NIC liability for this tax year and therefore do not worry this payment is not lost. This will be offset against your PAYE/NIC due in the next quarter of this tax year.
Hope this helps.
Aman