补充协议英文通常称为SupplementaryAgreement，也可称为Addendum。它是指对于已经签署的合同或协议，在一定条件下双方达成的补充协议。这种协议通常是为了解决已有合同中的未尽事宜或者新出现的问题而制定的。
以下是补充协议英文的范本，供大家参考：
SupplementaryAgreement
ThisSupplementaryAgreement(the“Agreement”),effectiveasof[Date],isenteredintobetween[PartyA](“PartyA”)and[PartyB](“PartyB”).
WHEREAS,PartyAandPartyBpreviouslyenteredintoacertainagreement,[nameoforiginalagreement](the“OriginalAgreement”),dated[date];
WHEREAS,PartyAandPartyBhavefurthernegotiatedandagreedtomodifycertaintermsandprovisionsoftheOriginalAgreement;
NOW,THEREFORE,inconsiderationofthemutualpromisesandagreementssetforthherein,andforothergoodandvaluableconsideration,thereceiptandsufficiencyofwhichareherebyacknowledged,PartyAandPartyBherebyagreeasfollows:
1.[InsertanymodificationstotheOriginalAgreement]
2.[Insertanyadditionaltermsorprovisions]
3.AllothertermsandprovisionsoftheOriginalAgreementnotmodifiedbythisAgreementshallremaininfullforceandeffect.
4.ThisAgreementmaybeexecutedincounterparts,eachofwhichshallbedeemedanoriginal,butallofwhichtogethershallconstituteoneandthesameinstrument.
5.ThisAgreementshallbebindinguponthepartiesheretoandtheirrespectivesuccessorsandassigns.
6.ThisAgreementshallbegovernedbyandconstruedinaccordancewiththelawsof[Insertgoverninglaw].
INWITNESSWHEREOF,thepartieshaveexecutedthisAgreementasofthedatefirstwrittenabove.
[PartyA][PartyB]
By:_________________________By:_________________________
Name:_______________________Name:_______________________
Title:________________________Title:________________________
注意事项：
1.需要明确指出引用的原协议名称和日期；
2.补充协议需要具体说明修改或新增的条款和内容；
3.落款必须包含双方单位名称、日期、签署人信息、职位等。
了解补充协议英文常用语，有助于合同或协议的修改与完善，确保双方权益得以充分尽善尽美地维护。