参照电子发票指南 3.1 版附录 1 第 21 项，在适用情况下，”原始电子发票参考编号 “字段为必填字段。
该字段应包含受影响/调整的原始发票/单据的 IRBM 独有识别码编号。
它适用于借方、贷方或退款凭证电子发票的开具。
根据常见问题（FAQs）（2024 年 7 月 19 日更新） 第 39 题，如果要对实施电子发票之前开具的原始发票进行调整（即没有分配 IRBM 独有识别码），纳税人可以在 “原始电子发票参考号码 “数据字段中输入 “NA“。
因此，针对这种特殊情况
1. 对于电子发票实施后出具的与电子发票有关的贷方凭证：
贷方凭证必须包括其调整的原始电子发票的 IRBM 独有识别码编号。
客户申请贷记的时间（如 9 月或 8 月）不影响此要求。
贷方凭证仍应提及原始电子发票。
2. 对于实施电子发票后出具的与实施电子发票前的发票有关的贷方凭证：
您将在 “原始电子发票参考号 “字段中输入 “NA“，因为原始发票不会有 IRBM 独有识别码。
这种方法可确保将调整与电子发票系统内的原始交易正确挂钩，同时也提供了一种处理对电子发票实施前的交易进行调整的方法。
Referring to e-Invoice Guideline Version 3.1 Appendix 1, Item 21, the “Original e-Invoice Reference Number” field is mandatory, where applicable.
This field should contain the IRBM Unique Identifier Number of the original invoice/document affected/adjusted.
It applies when a debit, credit, or refund note e-invoice is issued.
Based on the Frequently Asked Questions (FAQs) (updated on 19 July 2024) No. 39, if adjustments are to be made to original invoices issued before the implementation of e-Invoice (i.e., no IRBM Unique Identifier Number has been assigned), taxpayers are allowed to input “NA” in the ‘Original e-Invoice Reference Number’ data field.
So, to address this specific scenario:
1. For credit notes issued after e-Invoice implementation that relate to e-Invoices:
The credit note must include the IRBM Unique Identifier Number of the original e-invoice it’s adjusting.
The timing of when the customer applies the credit (e.g. Sep or August) doesn’t affect this requirement.
The credit note should still reference the original e-invoice.
2. For credit notes issued after e-invoice implementation that relate to invoices from before e-invoice implementation:
You would input “NA” in the ‘Original e-Invoice Reference Number’ field since the original invoice won’t have an IRBM Unique Identifier Number.
This approach ensures proper linking of adjustments to original transactions within the e-invoice system while also providing a way to handle adjustments to pre-e-invoice transactions.
