My drawer was short last night. Where do I start looking?

Reports, Shifts and the POS. Every shift shows what should have been in the drawer, what was counted and the difference. The should be figure is the float, plus the cash the sales took, minus cash refunds and cash paid out. Card sales are not in it, because they never touch the tray. Then read that shift's movements: a paid out with no reason written on it is the usual answer.