合同中表示“立即”通常用forthwith，比at once和immediately要正式；而immediately在合同中表示“立即”时，通常有固定用法，即immediately available funds”(立即可用的资金)，还可以表示“date immediately preceding......”(某日期前的那一天)等

例句1

In the event of termination by the Company and/or the Purchasers pursuant to Section XXX hereof, written notice thereof shall forthwith be given to the other Party and this Agreement shall terminate, and the purchase of the Purchased Shares hereunder shall be abandoned and rescinded, without further action by the Parties hereto.

如果公司和/或买方按照本协议第XXX条终止，应立即向其他方发出书面通知，本协议应当终止，并且在本协议下购买的所购股份应当被放弃和撤销，而无需本协议各方采取进一步行动。

例句2

The Issuer shall, not later than 10.30 a.m. (London time) on the Business Day immediately preceding each date on which any payment in respect of the Bonds becomes due, transfer or procure to be transferred in the manner provided for in Clause 2.3 to the Principal Paying Agent or to its order such amount as may be required for the purposes of such payment.

发行人应在各与债券有关的任何款项到期之日前一个营业日不晚于上午10:30（伦敦时间），以第2.3条规定的方式，将实现该付款目的所需的金额向主要付款代理或按其指令转账或安排他人向主要付款代理或按其指令转账。