销项负数发票（negative invoice），也称负数发票（即红字发票），是企业发生销售货物退回等业务时，冲减销售收入的合法凭证。对负数发票管理，税务机关一方面要对销货方纳税人开具的负数发票冲减销售收入合法依据进行审核，另一方面要对购货方纳税人是否按规定调减进项税额进行监督检查。红字发票和负数发票在本质上是一致的。只是由于实行电脑开票后，红字无法体现，才有负数发票之说。为了更好的理解该词，下面是该词的英文释义：A negative invoice is a type of credit note also referred to as a “negative balance invoice”.When crediting a buyer’s account to correct a payment error or when a purchase doesn’t perform to guaranteed standards, a business uses a negative invoice as legal documentation.

如：

As to the return of goods for which payment has been made, Party A agrees to issue a negative invoice and refund the payment to Party B at the same time; as to the return of goods for which no payment has been made, Party B shall pay the balance after deducting the price for the returned goods to Party A after Party A issues the negative invoice.

乙方已经支付款项的退货，甲方同意开具的销项负数发票同时向乙方退回退货款；乙方未支付货款的退货，甲方开具销项负数发票后，乙方向甲方支付扣除退货款后的金额。