Determine your tax role before the agent buys anything: if your platform is the merchant of record (MoR) for the transaction, you are responsible for calculating, collecting, and remitting tax; if the agent is buying from a third-party merchant, that merchant is the MoR and you are a buyer — your obligation shifts to receipt collection and expense reporting.
For MoR flows: integrate a tax calculation API (Stripe Tax, Avalara, TaxJar, or equivalent) to determine the correct tax amount at checkout time based on buyer address, product tax code, and nexus rules; never hardcode tax rates.
For buyer flows: configure the agent to request a VAT/GST receipt or tax invoice at checkout wherever the merchant provides one (this is often a checkbox in the billing address form or a post-purchase email opt-in); capture this receipt and store it linked to the purchase record.
Store receipts in a structured format alongside the transaction record: merchant name, transaction date, amount, tax amount, tax jurisdiction, and receipt document (PDF or URL); this is required for business expense claims and VAT reclaim.
For cross-border purchases: track the origin and destination jurisdiction for each transaction; VAT reclaim eligibility and tax treatment differ by jurisdiction and purchase category.
Run a monthly reconciliation pass to identify purchases missing a receipt or tax invoice; flag these for manual follow-up before the accounting close.
Known gotchas
Not all merchants issue proper VAT invoices automatically — some only provide a simple receipt; in jurisdictions requiring a full VAT invoice (with the buyer's VAT number) for reclaim, the agent may need to explicitly request one via a post-purchase flow.
Tax nexus rules change; a tax calculation API can become stale if not updated — ensure you are on a subscription plan that receives regular tax rate updates, not a static snapshot.
Marketplace purchases where the agent buys from a third-party seller on a platform may have split tax responsibilities between the marketplace and the seller; the receipt may show tax collected by the marketplace even though the merchant is the underlying seller — this complicates expense categorization.
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp