Research · Tool comparison · Living page
Substack vs Kit: the fee model comparison newsletter creators need
Short version: Both platforms are free to launch a newsletter. The fork is how they charge once readers start paying you. Substack takes 10% of subscription revenue as a platform fee, with no monthly bill and no subscriber cap. Kit charges 3.5% + 30¢ per paid subscription transaction, including on the free plan, which supports up to 10,000 subscribers. At $10/month subscriptions, Kit's per-transaction fee is about 35% cheaper than Substack's 10% cut. But Substack brings a built-in reader discovery network that Kit does not have. The decision usually comes down to two questions: do you want discovery built into the platform, and do you plan to run affiliate marketing alongside paid subscriptions?
The fee comparison
Substack and Kit both make money when your readers pay you, but through different mechanisms. Substack takes a percentage of gross revenue. Kit charges a flat per-transaction fee that does not scale linearly with revenue.
| Dimension | Substack | Kit |
|---|---|---|
| Monthly platform fee | $0 | $0 (Newsletter/free plan) |
| Platform cut on paid subscriptions | 10% of gross revenue | 3.5% + 30¢ per transaction |
| Subscriber cap (free) | No stated cap | 10,000 subscribers |
| Paid subscriptions on free plan | Yes (core feature) | Yes ("Sell digital products & subscriptions" stated on free plan) |
| Automations | Limited: welcome sequences, win-back campaigns noted; no workflow builder | 1 automation on free; unlimited on Creator ($33/mo+) |
| Affiliate links in email | ToS does not explicitly address affiliate links (neither permitted nor prohibited) | Permitted with restrictions: affiliate content allowed; 100%-affiliate sends excluded |
| Reader discovery network | Yes: Substack app, recommendations, trending content, reader-facing publications | No built-in reader discovery |
| Custom domain | Yes | Yes |
| API access | Limited; not documented prominently | Available; status on free plan unclear. Our July 2026 account test showed it working, but it is not listed as a free feature on the pricing page. |
One note on the fee comparison: Substack's stated fee is 10% of gross revenue "minus credit card fees" — meaning Stripe's processing fees come off separately after Substack takes its 10%. Kit's 3.5% + 30¢ is stated as the per-transaction fee on kit.com/pricing; whether this is all-in (including Stripe's portion) or a platform-only fee is not specified on the pricing page. Both platforms use Stripe for payment processing. When comparing the two, treat both fee figures as platform-level minimums, with underlying payment processing costs sitting beneath both.
Break-even math: when Kit's fee structure wins
The crossover point is determined by the per-transaction math. Substack's 10% scales linearly with revenue. Kit's 3.5% + 30¢ has a fixed component that matters more at low price points and less at higher ones.
| Subscription price | Substack platform fee (10%) | Kit platform fee (3.5% + 30¢) | Winner |
|---|---|---|---|
| $3/month | $0.30 | $0.105 + $0.30 = $0.405 | Substack |
| $5/month | $0.50 | $0.175 + $0.30 = $0.475 | Kit (marginally) |
| $10/month | $1.00 | $0.35 + $0.30 = $0.65 | Kit |
| $50/year ($4.17/mo equivalent) | $5.00 (billed once) | $1.75 + $0.30 = $2.05 (billed once) | Kit |
| $100/year ($8.33/mo equivalent) | $10.00 (billed once) | $3.50 + $0.30 = $3.80 (billed once) | Kit |
The break-even price point is approximately $4.62/month (below this, the 30¢ fixed fee makes Kit more expensive per transaction; above it, Kit is cheaper). The most common newsletter subscription price points ($5/month or $50-$100/year) all sit above the break-even, which means Kit's fee structure is cheaper at those price points for every subscriber.
This math applies to the Kit free plan. If you upgrade to Kit Creator ($33/mo) for unlimited automations, you need to fold that monthly fee into the comparison. At $10/month subscriptions, Kit Creator breaks even over Substack when your platform-fee savings exceed $33/mo. At $0.35 savings per subscriber ($1.00 − $0.65), that is roughly 95 paying subscribers. Above that, Creator saves money vs. Substack; below it, Substack's zero monthly fee wins.
Where Substack wins
Built-in discovery. Substack has a reader-facing app, recommendations, and trending content. When you publish on Substack, readers browsing the Substack network can find you. Kit is an email tool; there is no equivalent reader discovery layer. If organic growth through platform discovery matters to your model, Substack has a real structural advantage that does not appear in a fee table.
No subscriber ceiling. Substack has no stated free subscriber cap — you can build to any size without paying a platform fee until readers subscribe at a paid tier. Kit's free plan caps at 10,000 subscribers (a high ceiling, but a ceiling). For publications expecting to grow very large on the free/ad model before launching paid subscriptions, Substack removes one ceiling.
Simplicity. Substack is purpose-built for publishing. The writing experience, subscription setup, and reader payments are all one thing. Kit is a broader email tool with creator-monetization features added on; the full feature set is more complex.
Where Kit wins
Fee structure at typical price points. At $5-$10/month subscriptions, the range most creator newsletters use, Kit's 3.5% + 30¢ is meaningfully cheaper than Substack's 10% per transaction. Annual plans ($50-$100) show an even larger gap. The difference compounds with subscriber count.
Explicit affiliate policy. Kit's acceptable-use policy explicitly addresses affiliate links in email: permitted, with the restriction that 100%-affiliate-content sends are excluded. Substack's ToS (retrieved July 27, 2026) does not specifically address affiliate marketing; it neither permits nor prohibits it. If affiliate revenue is part of your model alongside paid subscriptions, Kit's written policy gives you a defined operating boundary. Our full affiliate-in-email comparison covers this for multiple platforms.
Automation. Kit's Creator plan includes unlimited automation sequences: behavioral triggers, tagging, segmentation, multi-step welcome sequences. Substack offers welcome sequences and win-back campaigns but not a general-purpose automation builder. If you are building sequences for different subscriber segments or automating based on reader behavior, Kit's toolset is deeper.
Owned audience, different export posture. Both platforms let you export your subscriber list. Kit's export is straightforward CSV from the dashboard. Substack's export works, but subscribers who paid via Substack's payment flow have a different relationship to the platform. Some creators have noted friction when migrating paid subscribers off Substack. This is anecdotal and not a documented policy difference, but worth researching before committing.
Which situations point to each
Substack makes more sense if: you want readers to find you through the Substack network; your subscription price is below $5/month; you want the simplest possible setup with no separate email tool; or you are not planning to do affiliate marketing.
Kit makes more sense if: your subscription price is $5/month or higher (Kit's per-transaction fee will be lower at those price points); you plan to include affiliate links in your newsletter and want an explicit policy; you need automation sequences beyond a basic welcome email; or you want to run your newsletter alongside other creator revenue like courses or digital products on the same platform.
What this page does not cover
Design and editing experience: both are functional, and the right choice depends on personal workflow preference. Substack's writing experience is frequently described as cleaner; Kit's email editor is more flexible for layout. We have not done a controlled comparison.
Substack Boost and network monetization features: Substack has introduced recommendation networks and referral features. These are distribution mechanisms, not fee-structure differences, and they change frequently enough that a living page would go stale. Check substack.com for current network features.
The "Substack Notes" social layer: Substack has added a social-feed product (Notes) that operates somewhat independently of the newsletter. It is a meaningful platform differentiator for creators whose growth model includes social content. We have not compared Kit's equivalent (none).
Sources
- Substack fee (10%) and free platform structure: substack.com/about, retrieved July 27, 2026. Down-rank: none (Substack's own first-party about page).
- Substack affiliate link policy: substack.com/tos, retrieved July 27, 2026. Finding: ToS does not address affiliate links. Separate Content Guidelines exist but were not directly accessible at the ToS URL.
- Kit transaction fees (3.5% + 30¢), free plan paid subscription support: kit.com/pricing, retrieved July 27, 2026. Down-rank: Kit is our affiliate partner; verify independently.
- Kit free plan subscriber cap (10,000), affiliate policy: first-hand account plus kit.com/pricing; see also our Kit free plan breakdown and affiliate-in-email comparison.
If you are choosing between Substack and Kit, our Kit affiliate link opens the free plan, which costs nothing and goes to 10,000 subscribers without a credit card. Substack has no sign-up fee either. Testing both with a small list before committing is a reasonable way to evaluate the writing and reader experience directly.