API · Manage · Entities
Create a tax election.
Files a tax election for the entity. Resolves to a jurisdiction-specific filing with the IRS or state authority and creates the corresponding Filing record. Returns 202 Accepted; final acceptance is delivered via webhook (tax_election.accepted or tax_election.rejected).
Supported kind values:
- `s_corp` — IRS Form 2553 (Election by a Small Business Corporation). Requires shareholder_consents listing every consenting stakeholder. Effective for the tax year specified by effective_date. - `section_83b` — IRC §83(b) election for restricted stock or restricted unit grants. Requires grant_id. Must be filed within 30 days of the grant; the API rejects late elections with 422 election_window_closed. - `check_the_box` — IRS Form 8832 (Entity Classification Election). Requires target_classification and effective_date. - `late_election_relief` — Rev. Proc. 2013-30 relief for missed S-Corp / QSub / ESBT / QSST elections. Requires original_election_kind and reason_for_failure.
Once accepted, the election shows up in tax_profile (e.g. flips s_corp_election_status to accepted for an S-Corp election) and on the entity's Compliance view.
Returns 202 Accepted. On completion, emits one of: entity.state_changed, filing.accepted. Subscribe via `POST /v1/webhook_endpoints` to consume.
Last updated
Request Body
application/json
TypeScript Definitions
Use the request body type in TypeScript.
kindstringRequiredOne of
"s_corp""section_83b""check_the_box""late_election_relief""qsbs_attestation""accounting_method_change""consolidated_return_election""extension_request"effective_datestring<date>Requiredgrant_idstringOptionalRequired for section_83b.
target_classificationstringOptionalRequired for check_the_box.
One of
"c_corporation""partnership""disregarded_entity"original_election_kindstringOptionalRequired for late_election_relief.
One of
"s_corp""qsub""esbt""qsst"reason_for_failurestringOptionalRequired for late_election_relief. Free text describing the cause of the missed deadline.
qsbsobjectOptionalRequired for qsbs_attestation. Records the §1202 issuance-test
facts at the moment of attestation.
entity_gross_assets_at_issuanceobjectOptionalCurrency amount in the smallest unit (cents for USD).
amountintegerRequiredInteger in smallest unit. 100 = USD 1.00.
currencystringRequiredISO 4217 alpha-3, lower-cased.
entity_qualified_trade_or_businessbooleanOptionalPer IRC §1202(e), excludes service businesses (law, health, consulting, finance), banking/insurance, farming, mining, hospitality. Most software/SaaS qualifies.
qualified_at_issuancebooleanOptionalaccounting_method_changeobjectOptionalRequired for accounting_method_change (Form 3115).
from_methodstringOptionalOne of
"cash""accrual""hybrid"to_methodstringOptionalOne of
"cash""accrual""hybrid"section_481a_adjustmentobjectOptionalCurrency amount in the smallest unit (cents for USD).
amountintegerRequiredInteger in smallest unit. 100 = USD 1.00.
currencystringRequiredISO 4217 alpha-3, lower-cased.
extension_requestobjectOptionalRequired for extension_request (Form 7004).
return_formstringOptionalextended_due_datestring<date>Optionalestimated_tax_dueobjectOptionalCurrency amount in the smallest unit (cents for USD).
amountintegerRequiredInteger in smallest unit. 100 = USD 1.00.
currencystringRequiredISO 4217 alpha-3, lower-cased.
metadataobjectOptionalFlat string-to-string map. Up to 50 keys. Keys: max 40 chars, charset
[A-Za-z0-9_\\-.]. Values: max 500 chars. Keys prefixed matter_ are reserved
for platform use. Metadata is retrievable but not filterable via query params.
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}/tax_elections" \ -H "Content-Type: application/json" \ -d '{ "kind": "s_corp", "effective_date": "2026-04-25", "shareholder_consents": [ "string" ], "grant_id": "grt_6XrTbVnZ", "share_lot_id": "string", "target_classification": "c_corporation", "original_election_kind": "s_corp", "reason_for_failure": "string", "qsbs": { "entity_gross_assets_at_issuance": { "amount": 50000, "currency": "usd" }, "entity_qualified_trade_or_business": false, "qualified_at_issuance": false }, "accounting_method_change": { "from_method": "cash", "to_method": "cash", "section_481a_adjustment": { "amount": 50000, "currency": "usd" } }, "extension_request": { "return_form": "1120", "extended_due_date": "2026-04-25", "estimated_tax_due": { "amount": 50000, "currency": "usd" } }, "metadata": {} }'const body = JSON.stringify({ "kind": "s_corp", "effective_date": "2026-04-25", "shareholder_consents": [ "string" ], "grant_id": "grt_6XrTbVnZ", "share_lot_id": "string", "target_classification": "c_corporation", "original_election_kind": "s_corp", "reason_for_failure": "string", "qsbs": { "entity_gross_assets_at_issuance": { "amount": 50000, "currency": "usd" }, "entity_qualified_trade_or_business": false, "qualified_at_issuance": false }, "accounting_method_change": { "from_method": "cash", "to_method": "cash", "section_481a_adjustment": { "amount": 50000, "currency": "usd" } }, "extension_request": { "return_form": "1120", "extended_due_date": "2026-04-25", "estimated_tax_due": { "amount": 50000, "currency": "usd" } }, "metadata": {}})fetch("https://api.mattermode.com/v1/entities/{id}/tax_elections", { 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}/tax_elections" body := strings.NewReader(`{ "kind": "s_corp", "effective_date": "2026-04-25", "shareholder_consents": [ "string" ], "grant_id": "grt_6XrTbVnZ", "share_lot_id": "string", "target_classification": "c_corporation", "original_election_kind": "s_corp", "reason_for_failure": "string", "qsbs": { "entity_gross_assets_at_issuance": { "amount": 50000, "currency": "usd" }, "entity_qualified_trade_or_business": false, "qualified_at_issuance": false }, "accounting_method_change": { "from_method": "cash", "to_method": "cash", "section_481a_adjustment": { "amount": 50000, "currency": "usd" } }, "extension_request": { "return_form": "1120", "extended_due_date": "2026-04-25", "estimated_tax_due": { "amount": 50000, "currency": "usd" } }, "metadata": {} }`) 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 = { "kind": "s_corp", "effective_date": "2026-04-25", "shareholder_consents": [ "string" ], "grant_id": "grt_6XrTbVnZ", "share_lot_id": "string", "target_classification": "c_corporation", "original_election_kind": "s_corp", "reason_for_failure": "string", "qsbs": { "entity_gross_assets_at_issuance": { "amount": 50000, "currency": "usd" }, "entity_qualified_trade_or_business": false, "qualified_at_issuance": false }, "accounting_method_change": { "from_method": "cash", "to_method": "cash", "section_481a_adjustment": { "amount": 50000, "currency": "usd" } }, "extension_request": { "return_form": "1120", "extended_due_date": "2026-04-25", "estimated_tax_due": { "amount": 50000, "currency": "usd" } }, "metadata": {}}resp = requests.post( "https://api.mattermode.com/v1/entities/ent_Nq3KcAbc/tax_elections", 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("""{ "kind": "s_corp", "effective_date": "2026-04-25", "shareholder_consents": [ "string" ], "grant_id": "grt_6XrTbVnZ", "share_lot_id": "string", "target_classification": "c_corporation", "original_election_kind": "s_corp", "reason_for_failure": "string", "qsbs": { "entity_gross_assets_at_issuance": { "amount": 50000, "currency": "usd" }, "entity_qualified_trade_or_business": false, "qualified_at_issuance": false }, "accounting_method_change": { "from_method": "cash", "to_method": "cash", "section_481a_adjustment": { "amount": 50000, "currency": "usd" } }, "extension_request": { "return_form": "1120", "extended_due_date": "2026-04-25", "estimated_tax_due": { "amount": 50000, "currency": "usd" } }, "metadata": {}}""");HttpClient client = HttpClient.newBuilder() .connectTimeout(Duration.ofSeconds(10)) .build();HttpRequest.Builder requestBuilder = HttpRequest.newBuilder() .uri(URI.create("https://api.mattermode.com/v1/entities/{id}/tax_elections")) .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("""{ "kind": "s_corp", "effective_date": "2026-04-25", "shareholder_consents": [ "string" ], "grant_id": "grt_6XrTbVnZ", "share_lot_id": "string", "target_classification": "c_corporation", "original_election_kind": "s_corp", "reason_for_failure": "string", "qsbs": { "entity_gross_assets_at_issuance": { "amount": 50000, "currency": "usd" }, "entity_qualified_trade_or_business": false, "qualified_at_issuance": false }, "accounting_method_change": { "from_method": "cash", "to_method": "cash", "section_481a_adjustment": { "amount": 50000, "currency": "usd" } }, "extension_request": { "return_form": "1120", "extended_due_date": "2026-04-25", "estimated_tax_due": { "amount": 50000, "currency": "usd" } }, "metadata": {}}""", Encoding.UTF8, "application/json");var client = new HttpClient();var response = await client.PostAsync("https://api.mattermode.com/v1/entities/{id}/tax_elections", body);var responseBody = await response.Content.ReadAsStringAsync();curl --request POST 'https://api.mattermode.com/v1/entities/ent_Nq3KcAbc/tax_elections' \ --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 '{ "kind": "s_corp", "effective_date": "2026-04-25", "shareholder_consents": [ "string" ], "grant_id": "grt_6XrTbVnZ", "share_lot_id": "string", "target_classification": "c_corporation", "original_election_kind": "s_corp", "reason_for_failure": "string", "qsbs": { "entity_gross_assets_at_issuance": { "amount": 50000, "currency": "usd" }, "entity_qualified_trade_or_business": false, "qualified_at_issuance": false }, "accounting_method_change": { "from_method": "cash", "to_method": "cash", "section_481a_adjustment": { "amount": 50000, "currency": "usd" } }, "extension_request": { "return_form": "1120", "extended_due_date": "2026-04-25", "estimated_tax_due": { "amount": 50000, "currency": "usd" } }, "metadata": {}}'const response = await fetch("https://api.mattermode.com/v1/entities/ent_Nq3KcAbc/tax_elections", { 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({ "kind": "s_corp", "effective_date": "2026-04-25", "shareholder_consents": [ "string" ], "grant_id": "grt_6XrTbVnZ", "share_lot_id": "string", "target_classification": "c_corporation", "original_election_kind": "s_corp", "reason_for_failure": "string", "qsbs": { "entity_gross_assets_at_issuance": { "amount": 50000, "currency": "usd" }, "entity_qualified_trade_or_business": false, "qualified_at_issuance": false }, "accounting_method_change": { "from_method": "cash", "to_method": "cash", "section_481a_adjustment": { "amount": 50000, "currency": "usd" } }, "extension_request": { "return_form": "1120", "extended_due_date": "2026-04-25", "estimated_tax_due": { "amount": 50000, "currency": "usd" } }, "metadata": {} }),});if (!response.ok) { throw new Error(`Matter API ${response.status}: ${await response.text()}`);}const data = await response.json();console.log(data);Response
application/json{
"id": "string",
"object": "tax_election",
"entity_id": "ent_Nq3KcAbc",
"kind": "s_corp",
"status": "pending",
"effective_date": "2026-04-25",
"filing_id": "flg_2x7Vc3Mn",
"document_id": "doc_PwQ7MmLk",
"grant_id": "grt_6XrTbVnZ",
"share_lot_id": "string",
"qsbs": {},
"target_classification": "c_corporation",
"shareholder_consents": [
"string"
],
"original_election_kind": "s_corp",
"reason_for_failure": "string",
"rejection_reason": "string",
"accepted_at": 1745539200,
"metadata": {},
"created": 1745539200,
"updated": 1745539200,
"livemode": false
}{
"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/not_found",
"title": "Not found",
"status": 404,
"code": "not_found",
"detail": "No entity with id `ent_Nq3KcAbc` is visible to this token.",
"doc_url": "https://mattermode.com/docs/guides/errors#not_found",
"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
}