Contracts are turned over to the buyer during their due diligence process. They agree to assume them or req to cancel, at which point you’ll need to send a termination notice to your vendor. Or if assumed, there should be a notice that you have in place to send letting them know of the sale/change in ownership and who they should send bills to new owner/buyer. However you need to check with the dept that handled the sale within your company to see what they agreed upon. There are also probably closing cr to buyer/seller in regards to taxes, ins, utilities, invoices, rents, etc.