Well of course he can, but I was moved to ask because he clearly can't follow a simple instruction from his party leader (and I'm not talking about 'Do not resign your seat and fight an ego-centric by-election').
Today, the Conservatives have published a list of the expenses claimed by their frontbenchers for the three month period just before Davis resigned. His expenses are therefore listed. One of the categories included was a tick box on whether any staff are family members. If so, the MP is asked to give their salary to within a 10k band (from this we learned that many Tory front benchers pay their wives up to 40k per year).
David Davis employs his wife Doreen and so he correctly ticked the family member box. However, in the box for her salary, he has written N/A (for not applicable).
Yes, it is a very petty thought. But this sort of cock up routinely costs ordinary people £100 fine from the revenue department. I am surprised, given the prominence given to this issue by the Tories (oppo day debate and everything) that they couldn't make sure their document was right before they launched it.