Methyl acetate (CAS 79-20-9, EC 201-185-2, UN 1231) is a saturated acyclic monoester with the formula CH₃COOCH₃ and a closed-cup flash point of −10 °C under ISO 3679:2015 or ASTM D56-21a. Under CLP Regulation (EC) No 1272/2008, Annex VI Table 3.1, the harmonised classification is Flam. Liq. 2 H225, Eye Irrit. 2 H319, and STOT SE 3 H336. The Harmonized System assigns the pure substance to heading 2915, subheading 2915.39, as an other ester of acetic acid. Customs entry problems are not typically caused by the absence of chemical data, but by mismatched data across the commercial invoice, dangerous goods declaration, packing list, and safety data sheet.

The first recurring documentation failure is a flash-point field mismatch. Dangerous goods declarations for Class 3 flammable liquids require the closed-cup flash point of the material as offered for transport, not a pure-substance value copied from a general safety data sheet. Methyl acetate at −10 °C and a normal boiling point of 57 °C at 101.3 kPa falls within Packing Group II because the flash point is below 23 °C and the initial boiling point is above 35 °C. A declaration entering Packing Group III on the assumption of a flash point between 23 °C and 60 °C produces a classification inconsistency that must be corrected before release. The same delay occurs when the proper shipping name is entered as “methyl acetate ester” or “MeOAc” instead of the regulatory name “Methyl acetate,” or when the UN number is transposed with 1173 for ethyl acetate.

Which Single Data Field Triggers the Most Methyl Acetate Entry Stops?

The field most often disputed in carrier rejections and binding ruling requests is the proper shipping name. Under 49 CFR 172.202(a)(1), the basic description must be entered as proper shipping name, hazard class, identification number, and packing group in sequence. The same obligation appears in ADR 5.4.1.2.1. For pure methyl acetate, the proper shipping name must appear as “Methyl acetate.” Synonyms such as “methyl ethanoate,” “acetic acid methyl ester,” and the abbreviation “MeOAc” are not accepted as substitutes for the regulatory proper shipping name. A second common failure is the use of UN 1993 Flammable liquid, n.o.s. for a pure product that has its own UN 1231 entry. The reverse failure occurs for formulated blends: an importer declares UN 1231 for a methyl acetate solvent mixture when the correct entry is UN 1993 with the technical names of the flammable components entered in parentheses.

The tariff misclassification risk is concentrated at the boundary between Chapter 29 and Chapter 38. Pure methyl acetate is an individual chemically defined compound of Chapter 29 and is classified by application of General Interpretative Rules 1 and 6 to heading 2915 and subheading 2915.39. A formulated solvent blend containing methyl acetate, methanol, ethyl acetate, or other solvents is not classified in subheading 2915.39 merely because methyl acetate is the principal component. If the blend is an organic composite solvent or thinner used in paints, cleaning, or degreasing, heading 3814 is often applicable. Declaring a blended mixture under 2915.39 triggers a tariff reclassification, a request for quantitative composition, and an audit cycle that extends beyond the terminal release window. The same distinction is maintained in the EU Combined Nomenclature, US Harmonized Tariff Schedule, and APAC national tariffs built on the Harmonized System.

Methyl Acetate Transport Classification and SDS Section 14 Alignment

The transport classification must be reproduced without variation on the multimodal dangerous goods declaration, the container packing certificate, and Section 14 of the safety data sheet. The entry in 49 CFR 172.101 and the UN Model Regulations for UN 1231 is Methyl acetate, Class 3, Packing Group II, label 3. Methyl acetate is not a marine pollutant under the IMDG Code. Its ADR classification code is F1, and the hazard identification number is 33. A recurring Section 14 defect is the omission of the closed-cup flash point test method. A flash point value without a method designation is rejected by carrier validation interfaces because GHS and transport flash point conventions are not identical. The appropriate closed-cup methods are ISO 3679:2015 and ASTM D56-21a. The boiling point of 57 °C, vapour pressure of 21.7 kPa at 20 °C, and relative density of 0.932 at 20 °C are the property data used by dangerous goods safety advisers to assess SDS fidelity. Methyl acetate undergoes slow hydrolysis in water to acetic acid and methanol; therefore, aqueous or co-solvent mixtures cannot be documented with pure-substance transport data without supporting mixture test results.

The documentation baseline for a compliant methyl acetate customs package is equality of chemical identity, proper shipping name, hazard class, packing group, flash point, HS subheading, and net quantity across the invoice, packing list, dangerous goods declaration, and SDS Section 14. The presence of CAS 79-20-9 on a commercial invoice does not remove the requirement to state the tariff subheading 2915.39 for the pure substance. For European entry, the REACH registration number or only representative reference must be available for non-EU manufacturers placing the substance on the market in quantities above 1 tonne per year under Article 8 of REACH. In US entry processing, the document set is reviewed against 19 CFR 141.61 invoice sufficiency criteria, 49 CFR 172.202 hazardous materials shipping paper requirements, and 49 CFR 172.604 emergency response information requirements. Entries that fail these cross-checks are routed to customs holds even when the chemical identity is not in dispute.

When Mixed-Solvent Shipments Fall Outside the Pure-Substance Flash Point Assumption

A customs paper file may be valid for pure methyl acetate and still fail for a formulated blend. A shipment described on the invoice as “methyl acetate 80%” but declared as UN 1231 can be rejected because UN 1231 applies to the pure chemical; mixtures containing methyl acetate should be evaluated under the UN Manual of Tests and Criteria, Part III, Section 32. The correct transport entry for many methyl acetate solvent blends is UN 1993 Flammable liquid, n.o.s. with methyl acetate and any other flammable components named as technical names, Class 3, Packing Group II or III depending on the measured flash point. The technical names must appear in the same field as the proper shipping name on the dangerous goods declaration. Failure to disclose the technical name triggers 49 CFR 172.202 and ADR 5.4.1.2.1 document rejections. The HS classification also shifts for blended solvents: a mixture prepared as a formulated cleaning solvent or thinner is classified under heading 3814 rather than 2915.39, because Chapter 38 covers prepared solvent systems not elsewhere specified. Importers that maintain separate tariff and transport records for industrial pure methyl acetate and formulated methyl acetate-based solvents reduce the number of entry flags.

A second mixture-related failure is the use of an SDS Section 14 that reports only the pure substance flash point, without the mixture flash point, boiling point, or composition range. When a methyl acetate blend contains water, the flash point cannot be assumed from the pure component. The mixture must be classified for transport and GHS using test data or established mixture rules under CLP. Published data for proprietary methyl acetate blends is limited; therefore, a customs broker cannot reconstruct the correct packing group from a generic solvent safety data sheet. A declared Packing Group III for a mixture with an actual closed-cup flash point below 23 °C creates a misclassification that may survive carrier acceptance and then fail at port state inspection. Documentation for such blends should include the quantitative formulation, the measured closed-cup flash point with method designation, and the regulatory packing group derived from that measurement. For pure methyl acetate, the corresponding data set remains unchanged: CAS 79-20-9, EC 201-185-2, UN 1231, Class 3, Packing Group II, HS 2915.39. For mixtures, the documentation must show the same identity discipline under UN 1993 and heading 3814 or the applicable tariff classification, otherwise the file is returned for correction at the container freight station.