What the number is, and who is responsible
VGM is the total mass of the packed container as presented for loading. It is not the cargo weight on the commercial invoice, and it is not the estimated weight used to quote. The shipper named on the bill of lading is responsible for obtaining and declaring it, even when a forwarder or warehouse actually weighs the box. National administrations enforce the rule; the carrier and terminal enforce it operationally by refusing to load.
The declaration has to reach the carrier in time for the stowage plan. That deadline is the VGM cutoff — usually earlier than SI cut and always before CY cut — because the planner cannot assign a stack position without a verified mass. A late VGM does not get 'worked around'; the container waits for the next sailing.
Method 1 vs Method 2
Method 1: weigh the packed, sealed container on a calibrated device — a weighbridge, a terminal scale, or certified lifting equipment. This is the default when cargo is heterogeneous, stuffed by a third party, or the shipper does not trust a calculated sum.
Method 2: weigh each package and item of cargo, add dunnage and packing, then add the container's tare mass from the CSC plate. Method 2 is only usable where the competent authority allows it and the shipper's process is documented. It fails in practice when tare is read from a booking instead of the plate, when dunnage is guessed, or when several suppliers stuff the same box and nobody owns the sum.
Tare, tolerance, and the worked check
Tare is stamped on the container's CSC safety-approval plate and often differs from the 'standard' 20-foot or 40-foot tare a desk keeps in its head. Using a library tare instead of the plate is a classic Method 2 miss. A 40-foot dry van might show 3,700 kg on one box and 4,200 kg on the next; that 500 kg error is enough to put a heavy export over a road limit or under a vessel's declared stack weight.
Worked check: 18 pallets at 850 kg each = 15,300 kg cargo. Dunnage and pallet wood 240 kg. Plate tare 3,980 kg. Method 2 VGM = 19,520 kg. If the booking estimated 18,000 kg 'cargo plus box', the stow plan and the trucker are both working off the wrong number. Weighing the packed container (Method 1) is how you catch that before the gate.
How VGM sits with the other three cutoffs
The four ocean cutoffs are VGM, SI, CY, and DOC. VGM is the physical constraint: terminals will not lift. SI is the documentary constraint: the carrier cannot draft a correct B/L. CY is the gate. DOC is the last amendment window. Missing VGM looks like a rollover even when the container is already in the yard, because the crane will not take it. That is why cutoff emails that only mention SI still need a separate VGM clock.
On a US export, VGM is also a Coast Guard / SOLAS enforcement matter. On a US import it does not replace ISF or AMS — those are customs security filings. Mixing the three in one 'docs deadline' reminder is how a desk files ISF on time and still rolls the box for want of a weight.