Document obligation errorsAuthorisation
CDS77004Reservation could not be made
HMRC explanation
What to check across the Document obligation errors
A document code needs further detail that is missing: an identifier, a status code, a quantity, a consignment reference, or a reason for a waiver. Check every document code on the item carries the details HMRC's explanation lists for it.
A declaration that clears CDS can still be wrong
The free eligibility checker confirms your import activity and whether a free post-clearance audit applies. No data upload, no commitment.
Source: HMRC, Customs Declaration Service error codes, Open Government Licence v3.0. GOV.UK publication · Licence