Top-up plans operate on a deductible basis. A deductible is the amount you need to pay out-of-pocket or through your base policy before the top-up plan starts covering the expenses. For instance, if your base policy has a coverage of $50,000 and your top-up plan has a deductible of $50,000 with an additional coverage of $100,000, the top-up plan will kick in only after the initial $50,000 is utilized.