One of the reasons they ask you to use their preferred purchasing card is that they can track spending across an organisation. Armed with this information, they can leverage better deals out of their suppliers based on the evidence of prior spending.When you put the charge on your personal card, your employer has no visibility of the spend, and can't use it as leverage in its negotiations with preferred suppliers.Most companies use Amex as their purchasing card -- sign up for Membership Rewards and you'll be fine.On the flip side, if you decide to use your personal card and your accounts payable department is slow (meaning you get charged interest), you probably won't get much sympathy for any extra cost this incurs or any financial hardship this puts you under. Your A/P team will politely point out that you haven't followed policy and put everything on your Amex, and you're out of luck...