No. It doesn't have to be a newly opened card and I would for sure call Chase before doing it (I will do this myself when we pull the trigger). In your account, there is usually a pay over time option for purchases over $100. If you click on that it will show you the monthly payments broken up into 6,12,18 months. If its a smaller amount but over $100 the options might be for 3,6,12 months only. Right now, for our account I have a charge there close to 1 K (from our recent Disney cruise) and when I click on the pay over time feature it is showing me 0 fees and 0 interest (I multiplied the monthly charge it was showing and it was coming up to be the total amount).Can I ask how did you get the 18 month pay over time with 0 fees? I have the chase Sapphire card, but I cannot find details about it this anywhere. Does it have to be a newly opened card?
From what I've been researching Chase right now is allowing your first pay over time plan to be 0 fees. If you create another plan after that on the same credit card then they charge you a 1.72% fee.
Again, it probably depends on the account but it might be worth looking into. I wish Chase would advertise this feature with the 0 fees. AMEX has 0 fees promo as well from time to time and they clearly advertise it (we took advantage of this with AMEX last year).
Edited to add: the pay over time feature should appear right next to the actual charge over $100