Hello Heather. First, what version of SAP Concur are you on? Is it Standard or Professional? This will make a big difference in answering your question.
Standard has a really easy way to exclude an Expense Type from Receipt requirements by using Compliance Controls.
Professional usually has an option for Receipt Handling that has a condition to exclude certain expense types from requiring receipts. The expense type you want needs to be added to this condition.
Feel free to send me a private message or send me your company name so I can look it up and see which option you'll need.