The benefit system is *so* complex, with significant amounts of benefits being awarded on a subjective rather than objective basis, that the results of user initiated queries would either be slanted towards the negative interpretation of circumstances(for instance, not including an award of Disability Living Allowance) which would restrict peoples ability to make informed decisions, or would have a positive slant which could be just as dangerous, encouraging people to make life changing decisions, which could turn out to be financially unsustainable once a real-life decision maker has decided to refuse a certain benefit.

I think on a privacy v computation v bandwidth trade-off, it would almost always make more sense to execute the rules locally than via a remote API. The guvmint could even multicast rules and updates to save further bandwidth.

For example, rather than get the tax computation rules, submit the minimum tax data into the gov’s real algorithm and get the result. I’m not talking about having a website where the user has to type in their name, address, job details, etc, but exposing the core API that would be used to calculate the tax anyway. This could be used by your application which makes multiple requests to the back-ends and produces a combined overview of your situation.