Sir,
Use of the previous year’s LUT Number in the shipment bill is a human error. You might have obtained the LUT for the current year since you have exported goods. So, you can go before the Customs Authorities for the shipping bill amendment with the relevant documents, especially the following.
Copy of Shipping Bill in original entries.
A letter from the exporter confirming the LUT reference detailing the discrepancy.
Copies of the previous and current years’ LUT.
A copy of the export invoice.
Any other supporting documents like export invoices, bills of lading, etc.
You can also take shelter under the CBEC Circular No. 37/11/2018-GST dated 15th March, 2018, in case of a refund issue.
Extract of the relevant portion of the Circular..
‘4.1. In this regard, it is emphasised that the substantive benefits of zero rating may not be denied where it has been established that exports in terms of the relevant provisions have been made. The delay in furnishing the LUT in such cases may be condoned and the facility for export under LUT may be allowed on an ex post facto basis, taking into account the facts and circumstances...’