According to the GST e-invoicing rules (as updated by NIC/GSTN):
For taxpayers with aggregate turnover above ₹10 crore, the invoice date must not be older than 30 days from the current date for generating an IRN (Invoice Reference Number).
For Example: If today is June 21, 2025, the invoice date must be on or after May 22, 2025.
If your invoice date is before May 22, 2025, the system won’t allow IRN generation.