What changed
An unnamed large marketplace partner told CarParts.com it will end the seller relationship when CarParts Connect, a Mirakl powered third-party marketplace, launches
When
Letter received October 2026; disclosed in the 10-Q filed October 30; reported November 10; CarParts Connect expected December 2026
Who it affects
CarParts.com (Nasdaq: PRTS); brands that sell on marketplaces while building their own marketplace or retail media network
What to do
Map revenue by channel, read each marketplace's seller agreement on competing activities, and plan a fallback before launching a rival channel

Key takeaways

  • A large unnamed marketplace partner told CarParts.com in October 2026 it will end the seller relationship when CarParts Connect launches, expected December 2026.
  • eBay and Amazon together were 30.3% of CarParts.com revenue in the first nine months of 2026, per Value Added Resource's reading of the 10-Q, far more than the $3.4 million year to date adjusted EBITDA.
  • Before launching a channel that competes with a marketplace you sell on, price the loss of that channel and build the fallback first.

How the CarParts.com dispute unfolded

  1. CarParts+ Rewards soft launch

  2. CarParts+ Rewards loyalty program launches

  3. CarParts Connect announced, powered by Mirakl

  4. Marketplace partner letter: conflict of interest

  5. Q3 results: sales $129.3M, adj. EBITDA $1.0M

  6. 10-Q filed with the partner disclosure

  7. CarParts Connect expected to launch

What CarParts.com disclosed

The disclosure sits in the executive summary of the management discussion in the 10-Q for the quarter ended October 3, 2026. The company says that if the partner terminates the relationship, "sales through this channel, could decline or cease", which could hurt its business and results. It says it expects to spend the coming weeks and months in discussions to find a solution, and that there can be no assurance those talks succeed. The filing does not name the partner or cite a contract clause or marketplace policy, and Value Added Resource reports that CarParts.com had not answered its questions on either point by publication.

CarParts Connect was announced on October 22, 2026 as "a new marketplace and retail media network" powered by Mirakl. The press release says it is expected to launch in December 2026, with seller recruitment starting immediately, and will cover accessories, travel and road trip gear, pet and passenger products, outdoor gear, electronics and car care as well as parts. The CarParts Connect seller page lists a commission of 15% that "can flex depending on category", no upfront cost and no exclusivity.

The numbers behind the risk

The quarter itself was CarParts.com's steadiest in a while. Net sales rose 1.2% to $129.3 million, gross margin improved to 33.4% from 33.1% on lower freight costs, the net loss narrowed to $4.1 million from $10.9 million, and adjusted EBITDA was $1.0 million, the third positive quarter in a row. For the first nine months net sales fell 7.1% to $396.9 million. The company ended the quarter with $33.8 million of cash and $25.5 million of convertible notes.

Against that base, the marketplace channel is large. Value Added Resource reports that the 10-Q puts eBay and Amazon at a combined 30.3% of revenue in the first nine months of 2026, about $120.3 million, down from 33.9% a year earlier. We could not read that line in the filing ourselves, so treat it as the outlet's reading. Even if the unnamed partner is only one of the two, losing it would remove a far bigger slice of sales than the company's year to date adjusted EBITDA of $3.4 million.

CarParts.com at a glance, 2026

$129.3MQ3 net sales, up 1.2%
33.4%Q3 gross margin
$3.4M9-month adjusted EBITDA
15%CarParts Connect commission
Source: CarParts.com Q3 2026 earnings release; CarParts Connect seller page

So what: a channel you rent can veto a channel you build

Many brands now want their own marketplace, retail media network or loyalty program; CarParts.com launched CarParts+ Rewards on October 13 and said more than 200,000 members had enrolled since a September soft launch. The lesson from this filing is that a marketplace can treat that move as competition and act on it, whatever the outcome of the talks. The surprise is the size of the bet: the new marketplace has no sales yet, while the channel at risk is already producing revenue.

The plain math for any brand: if a marketplace brings 30% of $50 million in annual sales, that is $15 million. A new owned channel at a 15% commission would need about $100 million of third-party seller sales a year to earn $15 million of commission revenue, before costs. That is why the order of operations matters: secure the fallback, then launch.

Worked example: pricing the downside first, illustrative numbers

A brand sells $20 million a year, with $6 million on one marketplace at a 25% contribution margin, so the channel contributes $1.5 million. The team plans its own niche marketplace. Before launch it reads the marketplace's seller agreement and finds a clause letting the marketplace end the relationship at will. It models a 60% recovery of lost buyers through its own site and other channels: it would still lose about $2.4 million of sales and $600,000 of contribution in year one. It then shifts more ad budget to its own site and a second marketplace for two quarters, so recovery is in place before launch rather than after a termination letter. The numbers are illustrative; the step is to price the worst case before the announcement.

What brands should do

Five steps for any brand thinking about a competing channel, or selling through a partner that might.

  • Finance lead: build a channel revenue and contribution table for the last 12 months, by marketplace, own site and wholesale. Metric: you know the exact dollars at risk if any one channel closes.
  • Legal or ops lead: read each marketplace's seller agreement and policies for termination at will and competing activities, and note the notice period. Metric: a one page summary of how each channel can end the relationship.
  • Marketing lead: before announcing a rival marketplace, retail media network or loyalty scheme, grow your own site and a second marketplace such as Walmart so they can absorb lost demand. Metric: no single marketplace above about a third of revenue.
  • Ads manager: keep branded search and retail media budgets ready to redirect if a channel closes. Metric: cost per order on the fallback channels stays within target.
  • Owner: if you sell parts or accessories on CarParts.com's new marketplace, keep listings live elsewhere too, since its launch date and partner talks are still open. Metric: share of your sales on any single platform.

Before you launch a rival channel

  • Map revenue and contribution by channel
  • Read termination and competing activity terms
  • Grow a second marketplace and your own site
  • Keep no single channel above a third of sales
  • Ready ad budgets to redirect demand
  • Price the worst case before announcing

When this does not apply

Most brands that open a Shopify store or a loyalty program are not building a third-party marketplace, and nothing in the filing suggests marketplaces object to that. The CarParts.com case is about a seller launching a rival platform for other sellers. The outcome is also not settled: the company says talks are ongoing, and the partner has not been named. If you want a channel risk review of your own mix, start with our free audit, and follow more coverage on the ecommerce marketplace news channel and in our multichannel selling tools report.

Sources

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