{"openapi":"3.1.0","info":{"title":"UK Self-Employed NIC API","version":"0.1.0","description":"UK Self-Employed NIC calculates the National Insurance a sole trader or partner pays on self-employed profits. class4_nic applies 6% to profits between the lower profits limit (GBP 12,570) and the upper profits limit (GBP 50,270) and 2% above, with the band workings. class2_nic and small_profits_threshold_check show the weekly Class 2 rate (GBP 3.65 in 2026-27) and whether profits reach the small...\n\nEvery operation is read-only or compute-only. The same tools are available over MCP (streamable HTTP) at https://uk-self-employed-nic.connectorbay.com/mcp.\n\nDisclaimer: General information only, not legal, tax, accounting or payment advice. UK Self-Employed NIC is an independent tool: it is not affiliated with, endorsed by or operated by any government body, central bank, standards body or scheme operator. Rates, thresholds and rules change; check the cited official source and confirm with a qualified professional before you rely on a result.","contact":{"name":"Unify Dynamics LLC","email":"agent@connectorbay.com","url":"https://connectorbay.com/uk-self-employed-nic/docs"},"termsOfService":"https://connectorbay.com/uk-self-employed-nic/terms"},"servers":[{"url":"https://uk-self-employed-nic.connectorbay.com"}],"externalDocs":{"url":"https://connectorbay.com/uk-self-employed-nic/docs"},"security":[{},{"bearer":[]}],"components":{"securitySchemes":{"bearer":{"type":"http","scheme":"bearer","description":"Optional. A Pro API key raises rate limits; no credentials are required."}},"schemas":{"Error":{"type":"object","properties":{"ok":{"const":false},"error":{"type":"object"}}}}},"paths":{"/v1/tools/class4_nic":{"post":{"operationId":"class4_nic","summary":"Class 4 National Insurance on self-employed profits: 6% between the lower and upper profits limits and 2% above. 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