> ## Documentation Index > Fetch the complete documentation index at: https://docs.scripxhq.com/llms.txt > Use this file to discover all available pages before exploring further. # Core concepts > The concepts every ScripX integration rests on: duty credit scrips, the Scrip Reference Rate (SRR), provenance screening, delivery-versus-payment settlement on ICEGATE with a UTR, and the GST-exempt HSN 4907 treatment of a scrip sale. Six ideas explain the whole platform. Read them once and every endpoint reads itself. ## Scrips A **duty credit scrip** is a transferable electronic credit from the Government of India that pays basic customs duty rupee-for-rupee. Exporters earn them as an export incentive; importers spend them against duty on imports. ScripX is the venue where the two sides meet. The two schemes are `RODTEP` and `ROSCTL`, the only values of the `scheme` enum across the API. See [What is a scrip?](/what-is-a-scrip), [RoDTEP explained](/concepts/rodtep-scheme), [RoSCTL explained](/concepts/rosctl-scheme) and the [Schemes annexure](/annexure/schemes). Three properties matter for integration: * **Scrips transfer whole.** A credit is not split in a sale. A buy requirement is covered by a bundle of whole credits, with any shortfall shown as `residual_paise`. * **Scrips expire.** Every credit carries a validity window, one year from creation in the customs ledger, unaffected by transfer. Unsold, unspent credits go to zero, which is why idle inventory gets sold. See [Scrip validity and expiry](/concepts/scrip-validity-expiry). * **Scrips transfer once.** A credit moves from its holder to one transferee with a valid IEC on ICEGATE, and not onward from there. Buyers buy to consume. See [Scrip transfer on ICEGATE explained](/concepts/scrip-transfer-icegate). ## The Scrip Reference Rate (SRR) The **Scrip Reference Rate** is ScripX's published benchmark price for scrips, by scheme and expiry band, every trading day. It is the anchor a firm quote is built from: every [quote](/api-reference/trading/quote) is one firm price benchmarked to the SRR, and a sell-side quote holds for a fixed firm window (`valid_until`). The SRR is published on the **public, no-key surface** so anyone can see the number the market is pricing against: * [`GET /public/rates`](/api-reference/public/rates), today's SRR per scheme with its methodology. * [`GET /public/rates/{scheme}/history`](/api-reference/public/rate-history), the daily series behind the number. * [`GET /public/rates/card`](/api-reference/public/rate-card), a plain-text rate card. The SRR is a benchmark published for information. A tradable price for an exact amount always comes from a [firm quote](/api-reference/trading/quote); never interpolate your own price off the index. ## Provenance screening No scrip is listed until it clears **provenance screening**. Before a credit can be quoted or sold, its origin is traced to the shipping bill it derives from, the selling firm is KYC-verified, and the credit's title and live status are confirmed in the ICEGATE ledger. For an integrator this reduces to one flag: a credit showing `sellable: true` on [a firm's credits](/api-reference/firms/credits) has passed screening and is safe to quote and trade. Buyers get provenance on every scrip without running the checks themselves. ## Delivery-versus-payment settlement ScripX settles **delivery-versus-payment (DvP)**: title and money move together, or neither moves. * Buyer funds are locked **before** the scrip moves. * The scrip transfers seller to buyer on ICEGATE. * The seller payout fires **on ICEGATE confirmation** of the transfer, by IMPS, with a UTR on the receipt, in minutes, same business day (**T+0**). * A settlement that cannot complete unwinds safely and refunds in full the same day. Your integration reads results rather than driving the rails: subscribe to [webhooks](/webhooks) for `order.matched`, `settlement.settled`, `settlement.failed` and `payout.sent`, or poll [positions](/api-reference/trading/positions). ## The UTR on every payout Every completed seller payout carries a bank **UTR** (Unique Transaction Reference). It is the auditable proof that money moved and the reconciliation key your finance team keys on. Payout events and the [audit export](/api-reference/account/audit-export) carry it through to the tamper-evident record. ## HSN 4907 and GST A scrip sale is **GST-exempt**: duty credit scrips fall under **HSN 4907**, exempt under Notification 02/2017. There is no GST on the scrip value to account for on the transfer. This is why `all_in_paise` on a [quote](/api-reference/trading/quote) is the whole story: it is the net number that changes hands, with nothing bolted on after. ## How the units work Three conventions hold on every endpoint: | Convention | Rule | Example | | ---------- | ------------------------------------------- | --------------------------- | | Money | integer **paise**, fields end in `_paise` | `100000000` is ₹10,00,000 | | Price | **bps of face value**, fields end in `_bps` | `9650` is 96.50% of face | | Time | ISO 8601 in **IST** | `2026-07-25T14:32:00+05:30` | Worked examples are in the [Money and price annexure](/annexure/money-and-price). ## Related * [Quick start](/quick-start), the market-to-order flow in five calls. * [Authentication](/authentication), the key, scopes and rate limits. * [Public rate index](/api-reference/public/rates), the SRR without a key. * [Price and discount explained](/concepts/scrip-price-discount), what actually moves the number. * [Glossary](/concepts/glossary), every term in the market with its API field. * [Terminology annexure](/annexure/terminology), every term the API reference uses, defined.