> ## Documentation Index > Fetch the complete documentation index at: https://docs.flowpayroll.ai/llms.txt > Use this file to discover all available pages before exploring further. # Submit EPS from monthly balances > Submit an EPS (Employer Payment Summary) to HMRC based on monthly balances for a specific tax year and month ## OpenAPI ````yaml /api-reference/specs/pay-api.yaml post /rti/eps/monthly-balances/{taxYear}/{taxMonth} openapi: 3.0.3 info: title: FlowPayroll API description: >- API for payroll management, including payroll upload, lock, HMRC submission, employee management version: 0.1.0 servers: - url: https://api.sandbox.flowpayroll.ai/v1 security: - XAuthToken: [] XOrgId: [] tags: - name: Employees description: >- Create, retrieve, update, and delete employee records, and look them up by NI number or payroll ID. - name: Starters & leavers description: Set and clear starter and leaver details, individually or in bulk. - name: Tax codes description: >- Manage employee tax codes and query the effective tax code and NI category on a given date. - name: NI & identifiers description: Manage NI categories, National Insurance numbers, and payroll IDs. - name: Student loans description: Start and end student and postgraduate loans. - name: Payroll setup description: Assign an employee's payroll config and set opening balances. - name: Payroll - name: Payroll lines - name: PayrollConfig - name: Pay Elements - name: Calculator - name: Payslip - name: RTI - name: YearEnd - name: Organisation paths: /rti/eps/monthly-balances/{taxYear}/{taxMonth}: post: tags: - RTI summary: Submit EPS from monthly balances description: >- Submit an EPS (Employer Payment Summary) to HMRC based on monthly balances for a specific tax year and month operationId: submitEpsFromMonthlyBalances parameters: - name: taxYear in: path required: true schema: type: integer minimum: 1800 maximum: 3000 description: The tax year to submit EPS for - name: taxMonth in: path required: true schema: type: integer minimum: 1 maximum: 12 description: The tax month to submit EPS for - name: preview in: query required: false schema: type: boolean default: false description: Whether to generate a preview without submitting to HMRC requestBody: required: false content: application/json: schema: type: object anyOf: - $ref: '#/components/schemas/FinalSubmissionDetailsY2024To2026Dto' - type: object description: Final submission details (optional) example: Final submission details for the period nullable: true responses: '200': description: EPS submission preview generated successfully content: application/json: schema: allOf: - $ref: '#/components/schemas/ResponseBody' - type: object properties: data: type: string description: The EPS submission XML preview example: ... '202': description: EPS submission triggered successfully content: application/json: schema: allOf: - $ref: '#/components/schemas/ResponseBody' - type: object properties: data: $ref: '#/components/schemas/EpsSubmissionEntryDto' '400': description: Invalid request body, tax year, or tax month content: application/json: schema: $ref: '#/components/schemas/ResponseBody' '500': description: Internal server error content: application/json: schema: $ref: '#/components/schemas/ResponseBody' components: schemas: FinalSubmissionDetailsY2024To2026Dto: type: object description: Final submission details for tax years 2024/2025 and 2025/2026 properties: becauseSchemeCeased: type: boolean nullable: true description: Indicates if the scheme has ceased example: true dateSchemeCeased: type: string nullable: true format: date description: 'The date when the scheme ceased (format: yyyy-MM-dd)' example: '2024-04-05' forYear: type: boolean nullable: true description: Indicates if this is the final submission for the tax year example: true ResponseBody: type: object properties: message: $ref: '#/components/schemas/MessageWithTokenResponse' content: type: object properties: data: type: object nullable: true metadata: type: object nullable: true properties: dateFormat: type: string default: yyyy-MM-dd dateTimeFormat: type: string default: yyyy-MM-ddTHH:mm:ss.fffZ paginationToken: type: string nullable: true validationIssues: type: array items: $ref: '#/components/schemas/ValidationIssue' messageToken: type: string EpsSubmissionEntryDto: type: object properties: submissionId: type: string description: The unique submission ID example: EPS_2025_001 taxYear: type: integer description: The tax year example: 2025 taxMonth: type: integer description: The tax month (1-12) nullable: true minimum: 1 maximum: 12 example: 6 organisationId: type: string description: The organisation ID example: org_123 hmrcEpsReportStatus: type: string description: The HMRC EPS report status enum: - NotSent - Sending - Sent - Failed example: Sent createdDate: type: string format: date-time description: Creation date example: '2025-01-01T00:00:00Z' createdBy: type: string description: User who created the record example: user_123 updatedDate: type: string format: date-time description: Last update date example: '2025-01-02T00:00:00Z' updatedBy: type: string description: User who last updated the record example: user_456 submissionBody: type: string description: The submission body nullable: true example: Submission body content correlationID: type: string description: The correlation ID nullable: true example: corr_123 submissionDate: type: string format: date-time description: The submission date nullable: true example: '2025-01-01T00:00:00Z' submissionResponse: type: string description: The submission response nullable: true example: Response from HMRC errors: type: array items: type: string description: List of errors nullable: true example: - Error message 1 - Error message 2 required: - submissionId - taxYear - organisationId - hmrcEpsReportStatus - createdDate - createdBy - updatedDate - updatedBy MessageWithTokenResponse: type: object properties: text: type: string token: type: string tokenArguments: type: array items: $ref: '#/components/schemas/ValidationIssueArgument' ValidationIssue: type: object description: > Field validation item. `reasonToken` is a stable snake_case key for i18n or custom client messages; `reason` is the default English text from the API. properties: field: type: string description: Dot-path of the field (e.g. name.firstName, address.line1). reason: type: string description: Default human-readable message. reasonToken: type: string description: Machine-readable error identifier (snake_case). reasonTokenArguments: type: array nullable: true items: $ref: '#/components/schemas/ValidationIssueArgument' ValidationIssueArgument: type: object properties: name: type: string value: type: string securitySchemes: XAuthToken: type: apiKey in: header name: X-Auth-Token description: Access token obtained from OAuth2 client credentials flow XOrgId: type: apiKey in: header name: X-Org-Id description: >- Organisation to scope the request to. Required when the principal can access more than one organisation; optional for single-organisation principals (the authorizer resolves it automatically). ````