Three Years After China's Stage IV Switch: Why Used Machinery Supply Is So Deep, and Why Thai Buyers Have Two Years Left on the BOI Under-5 Tier

The short answer first. Used construction machinery supply out of China is unusually deep in 2026 because of the non-road Stage IV switch on 1 December 2022: that made 2022 the last full Stage III model year. In the China supply pool we refresh daily (snapshot 29 Sep 2026, 1,874 units, sourced from live Tiebaobei used-machine listings), 1,606 units — 85.7% — were built in 2022 or earlier, while Stage IV units from 2023 onward number just 268, or 14.3%. The actionable slice for Thai buyers is the 588 units from 2021–2022 (31.4% of the pool; median DDP-Bangkok price THB 971,500, median 3,600 hours): they sit in the deepest supply band and still fall inside the under-5-year duty-exempt tier of Thailand's BOI Announcement 6/2558. That overlap closes. In 2027 the five-year line moves to 2022-and-newer and the 286 units from 2021 drop out; in 2028 it moves to 2023-and-newer and the 302 units from 2022 drop out too. After that, the BOI under-5 tier holds Stage IV machines only.

The policy deserves to be stated precisely. The Stage IV amendment to GB 20891-2014 took full effect on 1 December 2022, prohibiting the manufacture, import and sale in China of non-road diesel mobile machinery and engines at or below 560 kW that do not meet Stage IV (per the Ministry of Ecology and Environment's implementation notice of 29 November 2022). One common misreading needs clearing up: this is not a ban on continuing to operate or resell Stage III machines already in service — those remain legal inside China. What changed is that the new-machine pipeline is Stage IV only. Aftertreatment systems pushed new-machine acquisition cost up, owners' replacement cycles accelerated, and the displaced Stage III fleets moved in volume into the used and export channels. The deep supply is the result of that chain, not of any single prohibition.

The second driver is city-level emission control tightening through 2026, on dates that are quite specific. Shanghai bans non-road mobile machinery at Stage II and below city-wide from 1 January 2026. Beijing is phasing it in: from 1 July 2026, machines at Stage II and below or failing Class III opacity limits are barred in Dongcheng, Xicheng, Chaoyang, Haidian, Fengtai, Shijingshan and Tongzhou; from 1 December 2026 the ban extends city-wide. Guangzhou's revised notice took effect on 15 August 2026. Here too, the honest reading matters: the ban line currently stops at Stage II and below, so Stage III machines are still legal on Chinese sites. But the direction of travel in tier-one cities feeds straight into how owners price residual value — each step up squeezes older fleets out of the highest-margin urban projects and into the replacement and resale market.

Export figures confirm that supply is moving outward. Chinese construction machinery exports reached US$46.614 billion in January–August 2026, up 20.8% year on year; January–May was US$27.902 billion, also up 20.8%, against just 8% growth in the same period of 2025. On the lead product: 13,166 excavators of all types were exported in May 2026, up 34%, with first-half excavator exports up 33.5% cumulatively. One external condition is shifting, though. As Xinhua Finance reported on 25 September 2026, trade barriers are rising in developed markets — the EU opened an anti-dumping investigation into Chinese mobile cranes in December 2025, the UK imposed provisional anti-dumping measures on Chinese boom lifts in August 2026, and non-tariff hurdles such as Russia's scrappage tax and the EU carbon border levy are in play. No comparable measure currently applies to used construction machinery entering ASEAN, which is the practical reason Thailand and ASEAN remain the smoothest channel.

Price structure reads most clearly through the three BOI tiers. In the pool, under-5-year units (2021 and newer) number 856, or 45.7%, at a median DDP-Bangkok price of THB 975,000 and a median 3,600 hours. The 5–10-year band (2017–2020) is the thickest at 936 units, or 49.9%, median THB 887,000 and median 6,300 hours. Ten years and older (2016 and earlier) is down to 82 units, or 4.4%, median THB 630,000. A caution against reading the pool-wide medians literally: under-5 looks only 9.9% more expensive than 5–10, but that is a tonnage mix effect, not a real age premium. The same-model comparison is the honest one. Across 36 models with at least three comparable units on each side, the median age premium is 11.9%; on 20-tonne-class workhorses it is clearly larger — Sany SY205C, 11 under-5 units at a median THB 1,482,000 against 17 units at THB 1,190,000 in the 5–10 band (+24.5%); XCMG XE200DA, 11 units at THB 1,287,000 against 14 at THB 1,033,500 (+24.5%); LiuGong CLG920E, 6 units at THB 1,332,500 against 12 at THB 1,049,500 (+27.0%). Median hour meters run roughly 5,900–7,000 against 8,300–8,500.

What to pick depends on whether you are a BOI enterprise. If you are, the arithmetic is time-sensitive: lock in 2021–2022 units now, while supply is deepest and they still sit in the duty-exempt tier (588 units, median THB 971,500). Once the window closes, the under-5 tier holds Stage IV machines only — today 268 units at a median THB 1,056,000, 8.7% above those 588 units, out of a far thinner pool. For buyers not claiming BOI benefits the logic inverts: the 5–10-year band has the most units and the most negotiating room (936 units, median 6,300 hours). Two practical notes: imported used machinery under BOI requires an additional refurbishment report, and domestically-made used machinery does not qualify for the investment incentive (it must be imported used); and after a Promotion Certificate is issued, the machinery import window is generally 30 months, with extensions requiring approval from the Investment Monitoring Division — so do not schedule the window too tightly. We quote DDP only: the price already includes inland transport in China, export clearance, sea freight, Thai customs, duties and taxes, and inland delivery to your site — one landed number. Chinese-origin machinery under HS 8429 with a valid Form E normally attracts 0% import duty under ACFTA, with 7% VAT charged on landed value (final classification at clearance governs). Tell us your BOI status, machine class and tonnage, and budget range, and we will shortlist 2–3 units with year, hours and real photos.

Sources: Ministry of Ecology and Environment, 29 November 2022, notice on the countdown to Stage IV implementation for non-road mobile machinery (GB 20891-2014 Stage IV amendment, effective 1 December 2022); Shanghai Municipal People's Government notice adjusting the prohibited-use zone for high-emission non-road mobile machinery; Beijing Municipal People's Government notice designating prohibited-use zones for high-emission non-road mobile machinery; the corresponding Guangzhou municipal notice effective 15 August 2026; monthly 2026 export statistics from the China Construction Machinery Association and 21-sun industry press; Xinhua Finance, 25 September 2026, on construction machinery exports entering deeper water amid rising trade barriers; Thailand BOI Announcement 6/2558 and BOI machinery duty-exemption practice guidance. Pool figures are a snapshot of live listings refreshed 09:17 on 29 September 2026; THB prices use the same conversion basis as the rest of this site and move with the market.