Originally published May 12, 2026. Substantially rewritten and editorially reviewed September 8, 2026.
Selling through a marketplace and through your own website creates a practical software requirement: the system must preserve which sales belong to each channel and the evidence for who collects tax. A settlement total or a blanket "marketplace" flag is not enough to explain every transaction.
Use this guide to evaluate marketplace sales tax software with one period of your own data. The workflow checks are proposed procurement tests. The legal examples below are limited to California and Texas; they are not a nationwide threshold or filing table.
Separate the three decisions
For each state and sales channel, document collection responsibility, registration requirements and return reporting treatment separately. Record the applicable period and the authority used for the review.
A seller's own nexus does not, by itself, prove that the seller should collect again on a transaction for which a facilitator is responsible. Equally, facilitator collection does not establish that the seller has no obligations for direct sales.
California treats a registered or registration-required facilitator as the retailer for qualifying facilitated sales of tangible merchandise. Its guidance distinguishes those transactions from a seller's direct sales and describes a registration exception when all retail merchandise sales are through registered facilitators. CDTFA: Marketplace Facilitator Act.
Texas guidance makes the provider's certification important to the seller's collection treatment. It also distinguishes a Texas seller, who still needs a permit even with marketplace-only sales, from a remote seller selling solely through a provider that has certified it will collect. Texas Comptroller: Marketplace Providers and Marketplace Sellers.
These differences are a reason to ask for a state-specific review. Do not import one state's threshold, collection start date or reporting treatment into every state.
Assemble a period that includes both channels
Before a demonstration, assemble source orders, marketplace reports, settlement reports and accounting entries for the same agreed period. Include at least one direct sale, a facilitated sale, a return and an adjustment if those occur in your business.
Ask the vendor to preserve:
- Source order and line identifiers, transaction date and destination.
- Sales channel and the identity of the platform or facilitator.
- Gross sales, discounts, shipping, tax charged, platform fees and refunds as distinct amounts where the source provides them.
- The party shown as collecting tax and the source evidence for that classification.
- Settlement identifiers and dates that link receipts to orders.
- Review status and the reason for any manual correction.
A net payout is a cash settlement measure. It should not silently replace gross sales or taxable sales in a tax workpaper. Inspect how the integration handles fees, refund timing and orders that settle in a different period.
Keep the facilitator evidence with the decision
Request the relevant platform agreement, certification or other documented basis for collection responsibility. Keep its applicable dates and a retrievable copy with the review. An imported flag should point to this evidence rather than become the evidence itself.
California recommends retaining documentation that establishes the facilitator's responsibility and obtaining its permit or account number. The state also describes how a marketplace seller can purchase inventory for resale from its supplier. That purchase is a different transaction from the eventual sale to the end customer. CDTFA: Marketplace Seller Records and Purchases for Resale.
Keep supplier resale documentation, end-customer exemption evidence and facilitator collection evidence distinct in the evaluation. Do not accept a demonstration that treats any one of them as a universal substitute for the others.
Test the integration with concrete exceptions
Agree the expected treatment with your tax reviewer before running these suggested tests.
- Duplicate import: send the same marketplace order twice and inspect whether sales and tax totals change.
- Missing responsibility: remove the facilitator field or supporting evidence and inspect the review queue. The integration should make the missing information visible.
- Mixed channels: include direct and marketplace sales to the same state and confirm they remain distinguishable.
- Refund: trace a partial return to the original order, tax adjustment and settlement instead of applying an unexplained adjustment to a state total.
- Timing difference: put an order and its payout in different periods and explain the reconciliation.
- Changed platform terms: inspect how the applicable date and earlier review are preserved.
- Export: download the period's transaction detail and tie every exception to its source record.
A review queue is useful only if someone owns it. Ask who resolves each type of exception, what evidence is required and whether a correction changes calculation, reporting, settlement reconciliation or several of these.
Define what the purchased service includes
Calculation, marketplace data import, reconciliation, return preparation, filing and payment are separate deliverables. Ask the vendor to show the exact channels and jurisdictions supported by the proposal and document the work that your team or another provider will perform.
For any filing service in the proposal, confirm who authorizes submission and payment, how a failed submission is surfaced and what evidence of acceptance is returned. A prepared return or a payment instruction is not evidence of tax-authority acceptance.
Ask for an implementation estimate using your actual channel list and sample exports. Confirm how missing historical records, connector limitations and custom fields affect that estimate. Avoid a feature comparison that labels every integration "automatic" without testing the source data.
Choose the next evaluation step
Use the sales tax reconciliation buyer checklist for the period tie-out, and the sales tax software buyer's guide to structure the broader vendor evaluation.
If your project includes calculation integration, review the Prophit.ai sales tax API overview. Request a demonstration of the specific marketplace workflow before treating it as part of the implementation.
Compare the quoted costs in the software cost calculator. Keep the implementation scope and unresolved exceptions beside the price comparison so a lower quote does not conceal work that still belongs to your team.