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Starting October 19, 2026, Poshmark sellers are responsible for the full $50 USPS hazmat noncompliance fee if USPS flags their package. Until then Poshmark charged sellers $5 and covered the other $45. On Mercari, sellers have paid $25 of the $50 since September 1, 2026, and the most common trigger on both apps is an old hazmat marking on a reused box.
This post is part of our marketplace fee and policy changes tracker, which covers all seven marketplaces Sidekick Tools crosslists to.
Which platform changes on October 19?
The October 19 change is on Poshmark. In an October 5, 2026 blog post, Poshmark said that since USPS began charging the fee on July 12, it has covered most of it for sellers, and that “starting October 19, 2026, sellers will be responsible for the $50 fee if USPS flags their package” (Poshmark Blog, Oct 5, 2026).
Mercari’s change happened earlier, on September 1. Nothing about Mercari’s hazmat cost sharing changes on October 19. Mercari did change its prepaid label prices that day, which we cover in Mercari’s October 2026 shipping rate change.
What the USPS hazmat noncompliance fee is
USPS says a $50.00 hazmat noncompliance fee applies to commercial shipments that are improperly declared, improperly labeled or otherwise fail to meet its hazmat shipping rules (USPS: Shipping Restrictions & HAZMAT). Marketplace prepaid labels are commercial postage, so the fee can land on packages shipped with Poshmark or Mercari labels.
It’s a different charge from the hazmat handling fee. That one applies to packages that are properly declared as hazmat, and it costs $0 for Ground Advantage and $7.50 for Priority Mail or Priority Mail Express, according to the same USPS page.
A USPS Postal Bulletin notice adds two details. USPS assesses the noncompliance fee through its Census and Automated Package Verification processes, and the hazmat fees won’t be charged on USPS Returns service pieces until February 1, 2027 (USPS Postal Bulletin).
How Poshmark’s coverage changed in 2026
Poshmark phased this in over three months. Here’s the timeline, all from Poshmark’s own blog posts.
| Package postmarked | Seller pays if flagged | Poshmark pays | Source |
|---|---|---|---|
| Jul 12 to Jul 31, 2026 | $0 | 100% | Poshmark Blog, Jul 9, 2026 |
| Aug 1 to Oct 18, 2026 | $5 | $45 | Poshmark Blog, Jul 9, 2026 |
| From Oct 19, 2026 | $50 | Not covered | Poshmark Blog, Oct 5, 2026 |
The July post explained how a charge shows up. You get an email with the order details, the amount is deducted from your redeemable balance, and it appears in balance activity as “USPS charge for hazmat noncompliance.” If your balance goes negative, it corrects from your next sale or redemption. Poshmark also said back then that the fee applies to outbound seller shipments only, not returns, and that the $5 share was subject to change.
The October post doesn’t repeat the details about returns or how the charge is deducted. We’d expect them to work the same way, but check the Poshmark Support Center if a charge looks different.
How Mercari handles the hazmat fee
Mercari’s help center says that starting September 1, 2026, “Mercari and the seller split this fee evenly,” with Mercari covering $25 and $25 deducted from the seller’s earnings. Packages postmarked before September 1 were exempt from the seller side of the charge (Mercari Help: Why was I charged for an overweight or oversized package?).
Mercari describes the fee as applying when a non-hazmat item ships in a box that still has a visible hazmat label. It says correctly labeled hazmat packages aren’t affected by this change. Its advice for reused packaging is to remove or fully blot out old hazmat labels so none stay visible, and in another section it suggests turning the box inside out.
Mercari’s hazardous materials page adds a separate rule. Using a Mercari prepaid label to ship hazardous materials is prohibited except for the permitted types it lists, such as lithium batteries and aerosols, and USPS packages with those must go by Ground Advantage. Mercari also says that shipping hazardous materials with its prepaid labels makes the package ineligible for Shipping Protection (Mercari Help: Hazardous Materials).
What about eBay, Depop, Grailed, Whatnot and Etsy?
Whatnot says it still covers incorrect hazmat labeling adjustments on its labels for now, and will give notice before that changes (Whatnot Help: Review and appeal carrier adjustments). We didn’t find an official page from eBay, Depop, Grailed or Etsy that says how they pass the USPS fee through on their own labels.
What USPS does say is that the mailer is assessed the fee. If you buy your own commercial postage through a shipping service, plan on paying it yourself if a package gets flagged.
What gets packages flagged
Both Poshmark and Mercari say the most common cause isn’t the item inside. It’s the box.
- Old hazmat labels on reused boxes. Poshmark’s July post says to check all sides for hazmat stickers, warning symbols or old barcodes, and that partial coverage still counts as flagged.
- The “Limited Quantity” diamond. Poshmark calls out this small black-and-white diamond as easy to miss. It’s common on boxes that held beauty products, aerosols or cleaning supplies.
- Regulated items shipped without the right handling. Poshmark lists perfume, nail polish, aerosol sprays and electronics with lithium-ion batteries as regulated contents. USPS has its own rules for each, and some can only travel by ground.
How to avoid the fee
This is what we’d do before every shipment now:
- Look at all six sides of a reused box. Turn it over. The diamond often sits on the bottom or a side flap.
- Remove the marking or cover it completely. Use opaque tape or a plain label over the whole marking. Poshmark says partial coverage still counts.
- Turn the box inside out if it’s covered in old printing. Mercari suggests this directly.
- When in doubt, use a new box or poly mailer. Poshmark says the same thing. A pack of mailers costs less than one $50 charge.
- Check before you list regulated items. If you sell fragrance, nail polish or electronics, read the USPS hazmat rules and each marketplace’s hazardous materials policy first.
- Watch your balance activity. If you think a package was flagged by mistake, Poshmark says to contact Poshmark Support.
What this means for crosslisters
If you crosslist, the same box could cost you $50 on Poshmark, $25 on Mercari, or a different amount on another app, depending on where the item sold. The easiest fix is to treat every reused box the same way no matter which marketplace the order came from. Keep a stack of plain mailers by your packing station for anything that once held beauty or cleaning products. Poshmark also has a shipping change coming on October 26, 2026: if a package over 5 lb ships without a label upgrade, Poshmark will deduct the upgrade cost from your earnings. Our guide to Poshmark’s heavy package rule has the weight bands and costs.
It’s also a good time to look at what you list in categories like fragrance and nail polish. You might decide those items are better on a platform whose label flow lets you declare them properly. Keep in mind that a fee like this doesn’t show up in the commission you see at checkout, so your real profit per sale can be lower than the fee calculator says if a package gets flagged.
Sidekick Tools helps with the listing side of this. You can list an item once, crosslist it to Poshmark, eBay, Mercari, Depop, Grailed, Whatnot and Etsy, and keep your prices in sync when you adjust for shipping costs. See how it works, check pricing, or learn about the Poshmark bot. To check your Poshmark payout on a given sale, use the free Poshmark fee calculator, or read our Poshmark shipping guide.
Frequently asked questions
Does the October 19 hazmat fee change apply to Poshmark or Mercari?
It applies to Poshmark. Starting October 19, 2026, Poshmark sellers are responsible for the full $50 USPS hazmat noncompliance fee if USPS flags their package. Mercari’s change happened on September 1, 2026, when Mercari sellers began paying $25 of the $50.
How much is the USPS hazmat noncompliance fee?
USPS charges $50.00 per package on commercial shipments that are improperly declared, improperly labeled or otherwise fail to meet its hazmat shipping requirements. USPS began charging it on July 12, 2026.
Why would my package get flagged if nothing inside is hazardous?
The most common reason is a reused box that still shows an old hazmat label or marking, such as the small black-and-white Limited Quantity diamond. Poshmark and Mercari both say a package can be flagged for the markings on the outside even when the item inside is harmless.
How do I avoid the Poshmark hazmat fee?
Check all sides of any reused box and remove or completely cover old hazmat labels and markings, including the Limited Quantity diamond. If you’re not sure a box is clean, ship in a new box or poly mailer instead. If you sell electronics, review Poshmark’s electronics shipping guide first.
What can I do if I think I was charged by mistake?
Poshmark says to contact Poshmark Support if you believe your package was flagged by mistake, and its team will look into it. Mercari sellers can reach Mercari through its help center.
Does the hazmat fee apply to returns?
Poshmark’s July 2026 post said the fee applies to outbound seller shipments only, not returns. USPS also says it won’t assess hazmat fees on USPS Returns service pieces until February 1, 2027. Check Poshmark’s Support Center for the current wording after October 19.
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Sources
All sources checked on Oct 19, 2026.
- Poshmark Blog, “USPS HAZMAT Fee Update: How to Avoid the $50 Fee,” Oct 5, 2026. https://blog.poshmark.com/2026/10/05/usps-hazmat-fee-update-how-to-avoid-the-50-fee/
- Poshmark Blog, “What’s New: USPS Policy Update,” Jul 9, 2026. https://blog.poshmark.com/2026/07/09/59935/
- Mercari Help, “Why was I charged for an overweight or oversized package?” (Hazmat Fees section). https://www.mercari.com/us/help_center/article/172/
- Mercari Help, “Hazardous Materials.” https://www.mercari.com/us/help_center/article/209/
- USPS, “Shipping Restrictions & HAZMAT.” https://www.usps.com/ship/shipping-restrictions.htm
- USPS Postal Bulletin, “DMM Revision: Hazmat Handling and Noncompliance Fees.” https://about.usps.com/postal-bulletin/2026/pb22709/html/updt_002.htm
