Contact MarginBase
Last updated: July 2026
We read every message. There is no contact form and no account — email is the fastest way to reach us. Calculators run in your browser; we never receive the numbers you type unless you paste them in your email. For fee questions, a screenshot of your seller fee schedule (with account details cropped out) helps more than a vague “rates are wrong.”
Include the page URL and, for calculator issues, the inputs you used so we can reproduce the result.
What to write about
- Wrong markup, margin, break-even, or sales-tax formula
- Marketplace fee default that no longer matches a public schedule
- Broken link, layout issue, or accessibility problem
- Privacy question about analytics or how data is handled
Incorrect pricing formulas are treated as urgent once we can reproduce them from the inputs you send.
What we cannot help with
We cannot set your retail prices, file sales tax, negotiate marketplace fees, or reconcile your seller payouts. For books and filings, use a bookkeeper or tax professional; for fee disputes, use the platform’s support.
Privacy & legal
See our privacy policy for how the site handles analytics and third-party services. Terms of use are on the terms page. Methodology and citations live on methodology.