It's a while since I've done that, so I can't really help but I seem to remember that it was relatively expensive compared with the annual cost of the policy, the reason, I think, is that it's largely an administration cost. The message is: look into the cost of adding him permanently rather than just for a short period. It may only cost a trivial amount more and if you want to do it again before the policy renewal it could work out cheaper. The other thing is that it can actually be cheaper to have 2 people on a policy than just 1 so, if you are the only person currently named on your policy, it might be cheaper for future renewals. A colleague of mine said he rang his insurance company to take his wife off the policy at renewal because she was giving up driving (voluntarily, not compulsory); his insurer told him to leave her on, so long as her licence was still valid, otherwise his premium would increase.