Polyethylene terephthalate (PET) shipments entering major customs territories require a documentary set that aligns with Harmonized System classification, preferential origin status, and, for post-consumer recycled grades, chain-of-custody verification. The certificate of analysis (COA) is the central technical document; it records intrinsic viscosity (IV), density, diethylene glycol (DEG) content, acetaldehyde (AA), carboxyl end groups (CEG), and moisture. For a bottle-grade resin, the COA typically reports an IV of 0.80–0.84 dL/g when measured by ASTM D4603-18 or ISO 1628-1:2021, a solid-state density of 1.40–1.41 g/cm³ under ISO 1183-1:2019, and a melting peak of 245–247 °C by differential scanning calorimetry under ISO 11357-3:2018. Customs authorities do not treat these fields as routine quality notes; they use the viscosity number threshold of 78 mL/g to separate HS subheading 3907.61 from 3907.69. Because the COA is the primary evidence for that threshold, missing units, non-ISO-equivalent methods, or unsigned laboratory revisions routinely delay clearance even when the physical resin is unchanged.

For textile-grade PET, the COA profile differs: IV may be 0.62–0.68 dL/g, DEG 2.0–2.5 wt%, and melting point slightly lower due to comonomer incorporation. The same customs heading applies, but the COA still must support the declared grade because a textile-grade lot cannot be sold into a bottle-grade declaration without triggering a misclassification risk. The reviewing officer may compare the reported IV against the invoice line description; a line item stating “PET bottle-grade” with an IV of 0.64 dL/g is an internal inconsistency.

What COA Fields Face Rejection at PET Import Clearance?

Three COA fields are most likely to trigger a customs laboratory query: intrinsic viscosity, DEG/CEG ratio, and residual acetaldehyde. Intrinsic viscosity must be linked to a stated method and solvent temperature; a value of 0.80 dL/g in a phenol/1,1,2,2-tetrachloroethane solvent at 30 °C is not directly exchangeable with a value obtained in dichloroacetic acid at 25 °C. When the viscosity number is close to the 78 mL/g HS threshold, customs laboratories may request replicate measurements according to ISO 1628-1:2021 or ASTM D4603-18. DEG values above 1.5 wt% indicate copolymer modification that may affect classification or downstream performance, while CEG values above 35 meq/kg can signal hydrolytic or thermal degradation during storage. For carbonated soft-drink preforms, residual AA is usually specified below 1 ppm; a COA reporting 3–5 ppm without a purge-and-trap GC method reference does not prove food-contact suitability and may be rejected if the import declaration cites food-grade end use.

Acetaldehyde is particularly sensitive to sample preparation; the COA must specify whether the value was obtained from a predried pellet or a nitrogen-purged melt. A value of 0.8 ppm from a purge-and-trap headspace system is not directly comparable to a value of 3 ppm from a melt-injection GC method because the latter can generate AA through thermal decomposition. Customs rejections are frequently triggered not by an out-of-spec value but by method ambiguity. A COA that lists only “IV” with no solvent, temperature, or standard code prevents the reviewing officer from establishing equivalence with ISO 1628-1:2021. Similarly, moisture content determined by Karl Fischer titration must state whether the value is in weight percent or ppm; a resin lot at 0.4 wt% moisture is not equivalent to 0.4 ppm. In vacuum-dried PET, the moisture specification is typically below 50 ppm before injection moulding because residual moisture hydrolyzes the melt and reduces IV during processing.

Origin Evidence and Tariff Shift Mechanics for PET Polymer

Non-preferential origin for PET is determined under the substantial transformation criterion. Polymerization of purified terephthalic acid and monoethylene glycol into 3907.61 PET generally constitutes a sufficient transformation in most customs systems, but the importer must document the specific reactor location and the continuous polymerization stage. If the shipment is classified under 3907.69 because the viscosity number is below 78 mL/g, the origin file must still match the production lot in the COA; a lot of 0.75 dL/g resin cannot be moved into the 3907.61 heading by applying a correction factor.

Preferential origin claims require either the supplier’s declaration under the REX system, an EUR.1 movement certificate, or a USMCA certification of origin, depending on the free trade area. For PET, the tariff shift is generally from any other heading to 39.07, provided the polymerising reaction occurs entirely in the territory of one party. Cumulation is permitted under some agreements, but it introduces a second evidentiary layer: the producer must hold a valid supplier’s declaration for imported PTA under heading 2917.36 and MEG under heading 2905.31. A missing supplier’s declaration from the upstream monomer source breaks the origin chain even if the COA demonstrates full polymerisation at the declared site.

For European import clearances, the REX system uses a registered exporter number; a declaration with a REX number that does not appear on the consignment invoice or packing list will be queried. EUR.1 certificates must carry the correct origin criterion code and a customs stamp; an EUR.1 that lists only the bulk resin but not the lot numbers shown on the COA is vulnerable to a post-clearance origin verification. Similar document field alignment applies to USMCA, where the certifier does not need to file a certificate but must hold the supporting production records for the relevant period.

When the PET is sourced from a third country through a free trade zone, the origin documentation must also show whether the polymerization occurred before or after the good entered the zone. A batch that was melt-polymerised outside the preferential zone and only solid-state polymerised within the zone may not meet the tariff shift required by the agreement because solid-state polycondensation alone does not constitute a change to 39.07 from monomer. The same issue arises with toll-manufacturing arrangements: the origin certificate must name the toll producer that actually performed the polymerisation, not the trading company that resold the resin.

On a continuous solid-state polycondensation line operating at 205–215 °C with a dry nitrogen dew point below -40 °C, the COA should correspond to the finished silo lot rather than the amorphous melt-phase precursor. Production-scale shipments occasionally show batch-to-batch IV drift of ±0.015 dL/g across an 8–12 h SSP campaign. When the customs sample is drawn from a container exposed to ambient humidity above 60% RH at a tropical port, PET pellets can adsorb surface moisture and undergo hydrolytic degradation during the subsequent laboratory drying step. Such hydrolysis can shift a declared 0.82 dL/g resin to a measured 0.78 dL/g if bags were unsealed, placing it at the 78 mL/g classification boundary. The operational control is aluminium-lined packaging and retained reference samples from the same batch for customs arbitration.

When Recycled-Content Declarations Cross PET Customs Verification

Recycled-content declarations for PET are no longer purely commercial. Under EN 15343:2007, a supplier declaring post-consumer recycled content must hold a conformity certificate issued by an accredited certification body, with traceability to a specified recycling installation and an input mass balance for the claimed lot. ISO 14021:2016 requires the claim to be accurate, verifiable, and based on a documented chain of custody; a customs auditor may request the mass balance records showing the weight ratio of post-consumer flake to virgin polymer in the extrusion or solid-state feed. For food-contact recycled PET entering the EU, Regulation (EU) 2022/1616 adds a separate suitability layer: the recycling process must use an authorised process line, and the declaration of conformity must include the process and batch information. A customs declaration stating “recycled content 30%” without an attached certificate identifying the lot number, the declared mass balance, and the auditing body does not meet the substantiation expectation.

Recycled PET does not have a separate Harmonized System subheading. The shipment is classified under 3907.61 or 3907.69 according to the same viscosity threshold. The recycled-content declaration is therefore not an alternative to the COA; it is an additional document that may be examined for consistency with the declared end use and the transaction value. A recycled-content certificate that lists an IV of 0.74 dL/g while the COA lists 0.82 dL/g creates a document conflict requiring correction before release. On a twin-screw compounding extruder with 40:1 L/D and vacuum venting at -0.08 MPa, a post-consumer flake feed can reduce intrinsic viscosity unless a chain extender or solid-state rebuild step is applied. The resulting COA must therefore report the measured IV after compounding, not the virgin feedstock IV.

Mass balance allocation is a critical failure point. In a continuous extrusion line fed by 85 wt% virgin PET and 15 wt% washed post-consumer flake, the output pellets may be designated as 30% recycled content under an attributed mass balance model, but customs may require the physical mass ratio unless the certification scheme explicitly permits attribution. Operators must declare which mass balance approach applies, because the certificate alone does not automatically harmonise with customs valuation and origin rules. Certificate schemes such as ISCC PLUS permit mass balancing across production outputs, but the importer must keep the mass balance period, product class, and positive list consistent with the COA lot records.

Routine customs laboratories cannot quantify post-consumer content in PET pellets directly. Near-infrared and marker-based systems can provide qualitative screening for certain tracer-doped polymers, but they are not accepted as primary evidence for a declared percentage in standard import clearance. The accepted evidence remains the audited mass balance under EN 15343 or an equivalent certification scheme, supported by purchase invoices for baled bottles, flake yield records, and process loss calculations. Published data for quantified customs verification of recycled content across all enforcement jurisdictions is limited; enforcement varies from full certificate recognition to request for recycle-bale input photography.

In multi-lot consolidated PET shipments, the paper audit is executed on the container manifest against each pallet lot. When the COA reports four production lots but the recycled-content certificate aggregates them under a single reclaimed-input mass balance, the reviewing officer may accept the aggregation only if the certificate includes a lot-level input table. Discrepancies in lot numbering between the COA and the recycled-content certificate are the most frequent formal verification trigger. Retention of reference pellets from each lot is therefore an operational control for resolving intrinsic-viscosity disputes under ISO 1628-1:2021.