Understanding Society User Support

I am currently working on a project in which we are using the Secure Lab version of Understanding Society. We are interested in keeping the households that are renters in council or social housing who are receiving housing benefits as our unit of analysis . We have seen that the variable w_renthb captures whether the household has received housing benefits or not but, when we cross tabulate it with the variable w_rent, which captures the net amount of last rent payment, we observe that all those households that report zero rent are computed as inapplicables in the housing benefits’ variable (w_renthb). However, we assume that if the reported rent is zero and they are computed as renters, it should mean that the housing benefits are actually covering the whole rent and therefore they must be under housing benefits. Are we right on this?