Wife missing NI contributions when I was working as a UKBC in Gibraltar

My wife came across a letter from HMRC dated April 2004 stating Voluntary National Insurance contributions may be short from April 1996 until April 2002. I was based as a UKBC with the MOD in Gibraltar from Feb 1996 until October 1999 and my wife and children accompanied me for the duration. During that time Child benefit was paid for my children but through my employer as I was employed and my wife was not. The total due was £1213.65. Is she entitled for the credit of those missing years?

Hi PatMc67.
Your wife may be able to apply for National Insurance Service Spouse credits.
She can apply via her Personal Tax Account:
Personal tax account: sign in or set up
By submitting form MODCA2.
Further information can be found here:
Apply for Class 3 National Insurance service spouse credits
Thank you.