Urgent. Please help. Do I need reference letter for co-op job？

[ruandro]

Hello everyone,

Just got ITA 2 days ago under CEC. Almost finished all the steps but it asks me to upload Employment Records for it. Do I need a reference letter for it or can I just use the contract as the employment records?
Or should I just put Co-op under study history instead of work history to avoid the confusion?

Thanks for the help!