> ## Documentation Index > Fetch the complete documentation index at: https://docs.bolta.io/llms.txt > Use this file to discover all available pages before exploring further. # Amend Tax Invoice - Change in Supply Cost > Pass the increase (+) or decrease (-) from the original as items. Provide each item's tax (`tax`) according to `taxType`. For detailed calculation examples, see the [Amendment types guide](/en/docs/api-introduction/amendment-guide#change-in-supply-cost). The API removes invisible characters from the request text but keeps tabs, line feeds, and carriage returns. It rejects supplementary characters above U+FFFF, such as emoji, with `400`. See [Unsupported characters](/en/docs/api-introduction/issuance-guide#unsupported-characters). ## OpenAPI ````yaml /openapi.en.yaml post /v1/taxInvoices/{issuanceKey}/amend/changeSupplyCost openapi: 3.1.0 info: title: Bolta API description: > The Bolta e-tax invoice API. [API Overview](/en/docs/api-introduction/overview) | [Authentication guide](/en/docs/api-introduction/authentication) | [Use cases](/en/docs/api-introduction/usecase-b2b) version: 1.0.0 servers: - url: https://xapi.bolta.io description: Bolta API server security: - basicAuth: [] tags: - name: Tax Invoice Issuance description: > Issue and amend e-tax invoices. [Calculating the issuance amount](/en/docs/api-introduction/issuance-guide) | [Amendment types](/en/docs/api-introduction/amendment-guide) - name: Tax Invoice Retrieval description: > Retrieve e-tax invoice results and request processing status, and download the PDF of an issued tax invoice. [Tax invoice PDF guide](/en/docs/api-introduction/tax-invoice-pdf) - name: Reverse Issuance description: > Request and manage reverse issuance of e-tax invoices. [Email-approval reverse issuance](/en/docs/api-introduction/usecase-reverse-email) | [Simple-approval reverse issuance](/en/docs/api-introduction/usecase-reverse-simple) - name: Cash Receipt description: > Issue, cancel, and check the status of cash receipts. [Cash receipt guide](/en/docs/api-introduction/cash-receipt-guide) | [Cash receipt webhooks](/en/docs/api-introduction/webhook-cash-receipt) - name: Business Registration Status description: > Check the registration status and tax type of a business registration number. Look up one number or up to 100 numbers at once. This API requires no issuer registration and no certificate. [Business registration status guide](/en/docs/api-introduction/business-registration-status) - name: Revenue and Expense description: > Retrieve the revenue and expense tax invoices of your own business in Bolta in the order they changed, and request a collection. Responses include documents issued through Bolta and documents collected from Hometax. You need a Standard plan or higher, and the calls deduct no points. Connect Hometax in the Bolta dashboard first. [Revenue and expense guide](/en/docs/api-introduction/revenue-expense) - name: Bank Account Transactions description: > Retrieve the bank accounts and transactions connected to your own business in Bolta, and request a sync. You need a Standard plan or higher, and the calls deduct no points. Connect bank accounts in the Bolta dashboard first. [Bank account transactions guide](/en/docs/api-introduction/bank-account-transactions) - name: Bank Account Holder description: > Look up account holder names with a bank code and an account number. One path takes a single account and the other takes up to 100 accounts at once. Each account that returns a holder name deducts 50 points. [Bank account holder guide](/en/docs/api-introduction/bank-account-holder) - name: Document Issuance description: > Issue National Tax Service certificates from Hometax or a certified copy of corporate registry, and download the original PDF. Hometax documents are issued only for the business that owns the API key, and you must register a joint certificate in the Bolta dashboard. A corporate registry is issued for the corporation in `corporationNumber` and needs no joint certificate. Supported corporation types are stock company, limited company, general partnership company, limited partnership company, limited liability company, incorporated association, incorporated foundation, medical corporation, cooperative (including social cooperative), and other corporate entity (such as a patent corporation). Each document deducts 500 points for Hometax documents, 1,000 points for a corporate registry view copy, and 1,500 points for a submission copy. [Document issuance guide](/en/docs/api-introduction/document-issuance) - name: Issuer description: > Register and manage businesses that act as tax invoice issuers. Certificate requirements depend on the issuance type. [Glossary](/en/docs/api-introduction/glossary) | [Delegated issuance](/en/docs/api-introduction/usecase-delegated) | [Brokered Tax Invoice Issuance](/en/docs/api-introduction/usecase-brokered) - name: Certificate description: > Register and manage issuer certificates. [Certificate registration](/en/docs/api-introduction/certificate-registration) paths: /v1/taxInvoices/{issuanceKey}/amend/changeSupplyCost: post: tags: - Tax Invoice Issuance summary: Amend Tax Invoice - Change in Supply Cost description: > Pass the increase (+) or decrease (-) from the original as items. Provide each item's tax (`tax`) according to `taxType`. For detailed calculation examples, see the [Amendment types guide](/en/docs/api-introduction/amendment-guide#change-in-supply-cost). The API removes invisible characters from the request text but keeps tabs, line feeds, and carriage returns. It rejects supplementary characters above U+FFFF, such as emoji, with `400`. See [Unsupported characters](/en/docs/api-introduction/issuance-guide#unsupported-characters). parameters: - name: issuanceKey in: path description: Issuance request identifier required: true schema: type: string - $ref: '#/components/parameters/TaxInvoiceClientReferenceId' requestBody: content: application/json: schema: type: object properties: date: $ref: '#/components/schemas/DateString' title: Write date description: Supply cost change date taxType: $ref: '#/components/schemas/TaxInvoiceTaxType' items: type: array minItems: 1 maxItems: 16 items: type: object properties: date: $ref: '#/components/schemas/DateString' title: Item supply date description: Item supply date name: type: string title: Item name description: Item name maxLength: 100 minLength: 1 unitPrice: type: - integer - 'null' title: Unit price description: Unit price minimum: 0 exclusiveMinimum: 0 examples: - 100 quantity: type: - integer - 'null' title: Quantity description: Quantity supplyCost: type: integer title: Supply cost description: Supply cost examples: - 1000 - -1000 tax: type: - integer - 'null' title: Tax description: Tax examples: - 0 - 100 - -100 specification: type: - string - 'null' title: Specification description: Specification maxLength: 60 description: type: - string - 'null' title: Item note description: Item note maxLength: 100 required: - date - name - supplyCost required: - date - taxType - items allOf: - $ref: '#/components/schemas/TaxInvoiceItemsByTaxTypeConstraint' examples: Taxable: x-parity-id: taxable summary: Taxable "Change in Supply Cost" amendment value: date: '2026-05-27' taxType: TAXABLE items: - date: '2026-05-27' name: Price adjustment unitPrice: null quantity: null supplyCost: -200000 tax: -20000 specification: null description: null Zero-rate: x-parity-id: zeroRate summary: Zero-rate "Change in Supply Cost" amendment value: date: '2026-05-27' taxType: ZERO_RATE items: - date: '2026-05-27' name: Zero-rate price adjustment unitPrice: null quantity: null supplyCost: -200000 tax: 0 specification: null description: null responses: '200': description: '' content: application/json: schema: type: object properties: issuanceKey: $ref: '#/components/schemas/IssuanceKey' description: The IssuanceKey of the amended tax invoice required: - issuanceKey headers: {} '400': description: >- Request validation failed or the client reference ID was reused. An API key cannot reuse a `Bolta-Client-Reference-Id` it has already used, regardless of the request content. The response `code` is `INVALID_REQUEST`. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '500': description: Internal server error content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' deprecated: false components: parameters: TaxInvoiceClientReferenceId: name: Bolta-Client-Reference-Id in: header description: >- Client reference ID for a tax invoice request. This header is optional. Enter a non-blank value between 1 and 255 characters. After this value is used with a tax invoice issuance API, the same API key cannot reuse it, regardless of the request content or endpoint. A duplicate returns `400 Bad Request` with `INVALID_REQUEST`. If you do not receive a response, do not resend the request. Check the accepted request with the [request status API](/en/api-reference/tax-invoice-retrieval/retrieve-tax-invoice-by-client-reference). required: false example: your-unique-reference-id schema: type: string minLength: 1 maxLength: 255 pattern: \S schemas: DateString: type: string format: date examples: - '2024-08-24' TaxInvoiceTaxType: type: string title: Tax type description: >- TAXABLE: taxable (e-tax invoice), ZERO_RATE: zero-rate (e-tax invoice), TAX_FREE: tax-exempt (invoice). For TAXABLE the item tax cannot be null; for ZERO_RATE every item's tax must be 0. For TAX_FREE every item's tax must be null or omitted. enum: - TAXABLE - ZERO_RATE - TAX_FREE examples: - TAXABLE - ZERO_RATE - TAX_FREE TaxInvoiceItemsByTaxTypeConstraint: type: object allOf: - if: properties: taxType: const: TAXABLE then: additionalProperties: true properties: items: items: additionalProperties: true properties: tax: type: integer required: - tax - if: properties: taxType: const: ZERO_RATE then: additionalProperties: true properties: items: items: additionalProperties: true properties: tax: const: 0 required: - tax - if: properties: taxType: const: TAX_FREE then: additionalProperties: true properties: items: items: additionalProperties: true properties: tax: type: 'null' IssuanceKey: type: string description: >- Issuance request identifier. Its format and length may change, so store the entire string as is. examples: - 8D529FAD3EBAE050B79CE943CCC7CEDE ErrorResponse: type: object description: The error response returned when an API request fails properties: code: type: string description: Error type identifier message: type: string description: Error description traceId: type: string description: Request trace identifier required: - code - message - traceId securitySchemes: basicAuth: type: http scheme: basic description: >- Append a colon to your API key, Base64-encode it, and put it in the header. Enter the API key as the username and leave the password empty. ````