Is it OK to blacken out the saving's account numbers of my husband and mine too?

How about the NI Number? I read before that when submitting original salary slips, the National Insurance Number can be blackened out in order to prevent identity theft but the new VAF4A forms asks for the NI number of the sponsor. If I blacken it out, what would I show as a proof?

I have lots of things on my mind, and I'm so confused right now. Wish you guys could help me. Thanks in advance.