If it is genuinely 0% with no hidden fees, and you have the discipline, installment is mathematically smarter, keep your cash working and pay the phone off slowly with money that is being eaten by inflation anyway. I do this. BUT there are big IFs. First, verify it is TRULY 0%, some deals have a "processing fee" or require a specific credit card that charges you, or the cash price is lower than the installment price (so you are paying a hidden premium). Ask "what is the cash price vs total installment price" and compare. Second, you must be disciplined enough to not blow the freed up cash on lifestyle, otherwise you just created a debt with nothing to show. Third, it uses up part of your credit card limit for months which affects your available credit. If all checks pass and you invest or keep the cash productively, installment wins slightly. If you are the type to lose track of commitments, just pay cash and enjoy owning it clean. For most people, the simplicity of cash is worth more than the tiny financial edge.