You can set up monthly withdrawal from your account for all of them. Call MS accounting to do that. Whether that will be a single or more withdrawals per month depends. If all your contracts consist of an original and add-ons to that in the same use year, it will all be one. If by multiple contracts, you mean you have separate ones with separate use years and members numbers (e.g., you bought one or more through resale and got a different use year), then that could be separate withdrawals for each contract.