Ubezpieczenie,a podatek to dwie rozne sprawy.Niema wplywu na wysokosc podatku brak numeru ubez.do czasu kiedy nia masz swojego NIN otrzymujesz od pracodawcy tzw tymczasowy numer.

If you are employed
you should tell your employer your number as soon as you know it
your employer will use it to advise HMRC what National Insurance Contributions they have deducted and paid over so that HMRC can record these on your National Insurance account.
These earn you entitlement to benefit. If your employer does not have the correct National Insurance number then there could be a delay in establishing how much benefit you should get when you claim.