If you are buying supplies from the campus store on behalf of a research group or your advisor, you might be able to use a Cornell group charge code (availability of these codes, and what they can be used for varies from group to group). Each research grant handled by Cornell, such as an NSF grant, is assigned a charge number, typically of the form Exx-xxxx, where each ``x" is a digit. If you have such a code, rather than paying you just tell the cashier you are charging it to a group and give them that number, your name and office/lab phone number, and your Cornell ID card. Purchases can be charged to a grant at the campus store and various shops on campus, such as those described in Section 3.2. Ask the faculty member for permission for each purchase in advance, and keep careful track of the receipts. The faculty member should also tell you who to turn the receipts in to (usually either the department's accounting office or the faculty member's administrative assistant).