API · Create · Entities
Efile83b election.
E-file a founder's Section 83(b) election electronically (not by mail). When a founder receives restricted stock at formation, 83(b) lets them elect to be taxed on the spread at grant rather than at vesting — a one-time election with a HARD, non-extendable 30-day deadline from the grant date. Matter dispatches it on the e-file rail so the window is never lost to a postal round-trip.
Gate. signed_election_document_id must reference a Document in this tenant, on this entity, that has reached execution_status: executed — the founder's signature on the election letter authorises Matter to e-file it. Not executed returns 409.
Mode branch. In live the Filing persists queued (provider irs_efile_83b, no acknowledgement) and a durable background job hands the work to the rail worker — nothing is submitted to the real IRS from this request; the customer-facing webhook filing.efiled fires on terminal state. In sandbox/test the deterministic stand-in completes synchronously with a labelled EFILE-SANDBOX-83B-... acknowledgement.
Sub-agent rail. Returns 202 Accepted with a SubAgentSession.
Errors: 400, 401, 409, 422, 429. See errors for the RFC 7807 envelope.
Last updated
Request Body
application/json
TypeScript Definitions
Use the request body type in TypeScript.
grant_idstringRequiredThe restricted-stock grant the election covers.
signed_election_document_idstringRequiredDocument.id of the founder-signed Section 83(b) election letter.
Must reach execution_status: executed before this endpoint
accepts the call.
taxable_yearintegerRequiredThe taxable year of the election (the grant year).
Response Body
application/json
application/problem+json
application/problem+json
application/problem+json
application/problem+json
application/problem+json
Request
curl -X POST "https://api.mattermode.com/v1/entities/{id}/filings/efile_83b_election" \ -H "Content-Type: application/json" \ -d '{ "grant_id": "grt_8RsLkq2T", "signed_election_document_id": "doc_9f2c41d6a8b0", "taxable_year": 2026 }'const body = JSON.stringify({ "grant_id": "grt_8RsLkq2T", "signed_election_document_id": "doc_9f2c41d6a8b0", "taxable_year": 2026})fetch("https://api.mattermode.com/v1/entities/{id}/filings/efile_83b_election", { method: "POST", headers: { "Content-Type": "application/json" }, body})package mainimport ( "fmt" "net/http" "io/ioutil" "strings")func main() { url := "https://api.mattermode.com/v1/entities/{id}/filings/efile_83b_election" body := strings.NewReader(`{ "grant_id": "grt_8RsLkq2T", "signed_election_document_id": "doc_9f2c41d6a8b0", "taxable_year": 2026 }`) req, _ := http.NewRequest("POST", url, body) req.Header.Add("Content-Type", "application/json") res, _ := http.DefaultClient.Do(req) defer res.Body.Close() body, _ := ioutil.ReadAll(res.Body) fmt.Println(res) fmt.Println(string(body))}import requestsheaders = { "Authorization": "Bearer sk_test_4eC39HqLyjWDarjtT1zdp7dc", "Matter-Version": "2026-06-10", "Idempotency-Key": "ee7c3a9b-3f1a-4d8e-9b2a-7c5e1f0a2d4b",}payload = { "grant_id": "grt_8RsLkq2T", "signed_election_document_id": "doc_9f2c41d6a8b0", "taxable_year": 2026}resp = requests.post( "https://api.mattermode.com/v1/entities/ent_Nq3KcAbc/filings/efile_83b_election", headers=headers, json=payload,)resp.raise_for_status()print(resp.json())import java.net.URI;import java.net.http.HttpClient;import java.net.http.HttpRequest;import java.net.http.HttpResponse;import java.net.http.HttpResponse.BodyHandlers;import java.time.Duration;import java.net.http.HttpRequest.BodyPublishers;var body = BodyPublishers.ofString("""{ "grant_id": "grt_8RsLkq2T", "signed_election_document_id": "doc_9f2c41d6a8b0", "taxable_year": 2026}""");HttpClient client = HttpClient.newBuilder() .connectTimeout(Duration.ofSeconds(10)) .build();HttpRequest.Builder requestBuilder = HttpRequest.newBuilder() .uri(URI.create("https://api.mattermode.com/v1/entities/{id}/filings/efile_83b_election")) .header("Content-Type", "application/json") .POST(body) .build();try { HttpResponse<String> response = client.send(requestBuilder.build(), BodyHandlers.ofString()); System.out.println("Status code: " + response.statusCode()); System.out.println("Response body: " + response.body());} catch (Exception e) { e.printStackTrace();}using System;using System.Net.Http;using System.Text;var body = new StringContent("""{ "grant_id": "grt_8RsLkq2T", "signed_election_document_id": "doc_9f2c41d6a8b0", "taxable_year": 2026}""", Encoding.UTF8, "application/json");var client = new HttpClient();var response = await client.PostAsync("https://api.mattermode.com/v1/entities/{id}/filings/efile_83b_election", body);var responseBody = await response.Content.ReadAsStringAsync();curl --request POST 'https://api.mattermode.com/v1/entities/ent_Nq3KcAbc/filings/efile_83b_election' \ --header 'Authorization: Bearer sk_test_4eC39HqLyjWDarjtT1zdp7dc' \ --header 'Matter-Version: 2026-06-10' \ --header 'Idempotency-Key: ee7c3a9b-3f1a-4d8e-9b2a-7c5e1f0a2d4b' \ --header 'Content-Type: application/json' \ --data '{ "grant_id": "grt_8RsLkq2T", "signed_election_document_id": "doc_9f2c41d6a8b0", "taxable_year": 2026}'const response = await fetch("https://api.mattermode.com/v1/entities/ent_Nq3KcAbc/filings/efile_83b_election", { method: "POST", headers: { "Authorization": "Bearer sk_test_4eC39HqLyjWDarjtT1zdp7dc", "Matter-Version": "2026-06-10", "Idempotency-Key": "ee7c3a9b-3f1a-4d8e-9b2a-7c5e1f0a2d4b", "Content-Type": "application/json", }, body: JSON.stringify({ "grant_id": "grt_8RsLkq2T", "signed_election_document_id": "doc_9f2c41d6a8b0", "taxable_year": 2026 }),});if (!response.ok) { throw new Error(`Matter API ${response.status}: ${await response.text()}`);}const data = await response.json();console.log(data);Response
application/json{
"sub_agent_session": {
"id": "string",
"object": "sub_agent_session",
"status": "pending",
"target_resource": {
"kind": "filing",
"id": "string"
},
"agent_kind": "de_sos_filer",
"target_url": "http://example.com",
"created_at": "2019-08-24T14:15:22Z",
"started_at": "2019-08-24T14:15:22Z",
"completed_at": "2019-08-24T14:15:22Z",
"outcome": {
"confirmation_number": "string",
"receipt_document_id": "string",
"error_kind": "string",
"error_detail": "string"
},
"actions_taken": [
{
"at": "2019-08-24T14:15:22Z",
"step": "string",
"detail": "string"
}
],
"livemode": true
},
"filing_id": "string"
}{
"type": "https://mattermode.com/docs/errors/invalid_request",
"title": "Invalid request",
"status": 400,
"code": "invalid_request",
"detail": "Request body could not be parsed as JSON.",
"doc_url": "https://mattermode.com/docs/guides/errors#invalid_request",
"request_id": "req_Qw9xYz8A"
}{
"type": "https://mattermode.com/docs/errors/authentication_required",
"title": "Authentication required",
"status": 401,
"code": "authentication_required",
"detail": "No bearer token was supplied. Pass `Authorization: Bearer sk_live_...` on every request.",
"doc_url": "https://mattermode.com/docs/guides/errors#authentication_required",
"request_id": "req_Qw9xYz8A"
}{
"type": "https://mattermode.com/docs/errors/invalid_state_transition",
"title": "Invalid state transition",
"status": 409,
"code": "invalid_state_transition",
"detail": "Entity ent_Nq3KcAbc is in state `dissolved`; `dissolve` is not a valid transition.",
"doc_url": "https://mattermode.com/docs/guides/errors#invalid_state_transition",
"request_id": "req_Qw9xYz8A",
"current_state": "dissolved",
"attempted_transition": "dissolve",
"allowed_transitions": []
}{
"type": "https://mattermode.com/docs/errors/dissolution_prerequisites_missing",
"title": "Dissolution prerequisites missing",
"status": 409,
"code": "dissolution_prerequisites_missing",
"detail": "Voluntary dissolution requires `board_resolution_id` and `stockholder_consent_id`, or `auto_generate_resolutions: true`.",
"doc_url": "https://mattermode.com/docs/guides/errors#dissolution_prerequisites_missing",
"request_id": "req_Qw9xYz8A"
}{
"type": "https://mattermode.com/docs/errors/valuation_stale",
"title": "409A valuation stale",
"status": 409,
"code": "valuation_stale",
"detail": "Active 409A val_AbCd1234 is older than 12 months or superseded by a material event. Issuing ISOs at the prior strike risks IRC §409A violation. Refresh via POST /entities/{id}/valuations/{id}/refresh_request.",
"doc_url": "https://mattermode.com/docs/guides/errors#valuation_stale",
"request_id": "req_Qw9xYz8A"
}{
"type": "https://mattermode.com/docs/errors/validation_failed",
"title": "Validation failed",
"status": 422,
"code": "validation_failed",
"detail": "One or more fields failed validation. See `errors[]`.",
"doc_url": "https://mattermode.com/docs/guides/errors#validation_failed",
"request_id": "req_Qw9xYz8A",
"errors": [
{
"field": "founders[0].equity",
"code": "out_of_range",
"message": "Equity must sum to 100% across all founders."
}
]
}{
"type": "https://mattermode.com/docs/errors/rate_limit_exceeded",
"title": "Rate limit exceeded",
"status": 429,
"code": "rate_limit_exceeded",
"detail": "Request rate exceeded for this key. Retry after `retry_after` seconds or honor the `Retry-After` header.",
"doc_url": "https://mattermode.com/docs/guides/errors#rate_limit_exceeded",
"request_id": "req_Qw9xYz8A",
"retry_after": 30
}