You should not have to ask a client to reimburse you for traveling expenses since you planned the wedding out of town and if you are a wedding planner then send the client a bill and if the bill is not paid within a month send another one. If the last bill sent is not paid then put it into a Collection Agencies hands. If you are not a wedding planner and did this on the side you can do the same thing, but go to small debts court.
