Many people haven't had occasion to ship with a courier company in their past, and aren't sure what the requirements are when the time finally comes where they have a need to ship something. Every Chicago courier service has different rules about this. Some of them are going to require that you open a full account with the company before you are allowed to ship anything. Others will have policies in place to make it possible for anyone to ship with them. There are advantages though to opening accounts if you predict more shipping in your future.
If a courier will allow you to ship something without an account, it is important to realize that there will be some requirements, and some limitations on your order. First of all, you will usually be required to pay for your shipment up front. This is because you don't have established credit with the company like account holders, to whom they simply bill shipping costs after they have shipped the packages.
Next, there are a variety of functions and features of the courier service which are usually offered only to those that have accounts in good standing with the courier company. This includes things like the ability to place orders online, and being able to receive electronic billing statements. If some of this more advanced functionality seems like it would be of use to you in the future, then it is worth considering opening a proper account with the courier.
There are some upsides to trying to ship with a few courier companies without an account before you actually decide on the company that is the right one for you to open an account with. This can serve as a sort of evaluation period, from which you can hopefully learn a few different things. You can use the shipping you do with companies without an account as a concrete way of comparing their costs. You can also get a better understanding of their differing customer service policies and find out which company you prefer doing business with.
You will be able to ship with a courier without opening an account with them if that is what you want to do. However, the advantages of having an account seem to suggest that if you're going to have regularly shipping needs, that you only use a few trial shipping efforts without an account as a means to find the best company.