收银机是一部仪器，由人手操作，设置于零售商店，由收银员打入每位顾客所购买的货品牌价，收银机会计算出其总消费金额。收银机是日记账式记录当天的所有贸易。在每天，商店休息前，店员会点算收银机内的实际现金额，再与机内的日记账（俗称蛇仔）总额比对，此为内部审计之一。通常收银机也打印收据给顾客，为保证每单交易在日记账必有记录。有不少店主提示顾客，购物必须要索取机印收据，若收银员收银后不打印收据，顾客可以向店主投诉。

A cash register, also referred to as a till in the United Kingdom and other Commonwealth countries, is a mechanical or electronic device for registering and calculating transactions. It is usually attached to a drawer for storing cash and other valuables. The cash register is also usually attached to a printer, that can print out receipts for record keeping purposes.