> ## Documentation Index
> Fetch the complete documentation index at: https://docs.arcuserp.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Apply a one-time reconciliation baseline (migration cutover anchor)
> Required API key scope: `accounting:write`
THE Baseline wizard executor (CLEARING-RECON-REENGINEER S6, 2026-07-01;
Xero conversion-balance + NetSuite go-live pattern). In ONE database
transaction it:
1. creates a COMPLETED system reconciliation session ("Migration
baseline") at `baseline_date` / `baseline_balance`,
2. bulk-marks the bank GL's unreconciled POSTED journal lines dated on
or before `baseline_date` as reconciled -- EXCEPT the operator-kept
in-transit `keep_open_gl_line_ids`,
3. bulk-excludes (`exclude_reason='pre_baseline'`) unreconciled bank
feed lines dated on or before `baseline_date` -- EXCEPT
`keep_open_bank_txn_ids`,
4. stamps `reconciliation_baseline_date` + `baseline_balance` on the
bank account (which then seeds new sessions' opening balance),
5. returns the flip/exclude counts + the variance math.
**Variance proof:** `variance = baseline_balance - (posted GL balance
at the anchor - kept-open in-transit total)`. A variance beyond $0.01
returns 422 with the full math unless `force: true`.
**Guards:** 409 `baseline_already_exists` when a different baseline is
already stamped (re-running with the SAME date + balance is idempotent
and returns the existing session with `already_applied: true`);
409 `reconciliation_in_progress` when an open session exists (cancel it
first via PATCH /accounting/reconciliations/{id}).
**Posts ZERO GL.** The only GL-adjacent effect is
`journal_entry_lines.reconciled_at` flips (the same GL-neutral signal a
normal match writes). No closed-period guard applies (the anchor date
is usually historical and nothing is posted).
Supports the `Idempotency-Key` header (canonical api-v1 mutation
contract) in addition to the parameter-level idempotency above.
## OpenAPI
````yaml /openapi.yaml post /bank-accounts/{id}/reconciliation-baseline
openapi: 3.1.0
info:
title: Arcus ERP Public API
version: 1.0.0
description: >
Arcus ERP public REST API. Designed for external integrations and data
migration.
**Authentication.** Bearer token (API key) via the `Authorization` header.
Format: `Authorization: Bearer ark_live_ent__` (or
`ark_test_*` for sandbox).
API keys are issued per-entity in **Settings > Developers > API Keys**.
**Entity scoping.** The entity is encoded in the API key prefix; routes are
flat
(e.g. `/v1/accounts`, `/v1/orders`, `/v1/products`). A small set of platform
endpoints
(migration, reconciliation, events, webhook endpoints, API keys) use the
`/v1/entities/{entity_id}/...` form -- those are noted in their tags.
**Key capabilities.**
- Related-resource hydration via `?expand[]=` (see `x-arcus-expand` on each resource).
- Cursor-based pagination (`starting_after` / `ending_before` / `limit`).
- Idempotency via the `Idempotency-Key` header.
- Webhook events for asynchronous notification.
- Conditional requests / ETag for cache validation.
servers:
- url: https://api.arcuserp.com/v1
description: Arcus ERP API (accepts both live `ark_live_*` and test `ark_test_*` keys)
- url: https://dev-api.arcuserp.com/v1
description: >-
Dev sandbox API (test-only data, accepts `ark_test_*` keys against dev
RDS)
security: []
paths:
/bank-accounts/{id}/reconciliation-baseline:
post:
tags:
- Accounting
summary: Apply a one-time reconciliation baseline (migration cutover anchor)
description: |
Required API key scope: `accounting:write`
THE Baseline wizard executor (CLEARING-RECON-REENGINEER S6, 2026-07-01;
Xero conversion-balance + NetSuite go-live pattern). In ONE database
transaction it:
1. creates a COMPLETED system reconciliation session ("Migration
baseline") at `baseline_date` / `baseline_balance`,
2. bulk-marks the bank GL's unreconciled POSTED journal lines dated on
or before `baseline_date` as reconciled -- EXCEPT the operator-kept
in-transit `keep_open_gl_line_ids`,
3. bulk-excludes (`exclude_reason='pre_baseline'`) unreconciled bank
feed lines dated on or before `baseline_date` -- EXCEPT
`keep_open_bank_txn_ids`,
4. stamps `reconciliation_baseline_date` + `baseline_balance` on the
bank account (which then seeds new sessions' opening balance),
5. returns the flip/exclude counts + the variance math.
**Variance proof:** `variance = baseline_balance - (posted GL balance
at the anchor - kept-open in-transit total)`. A variance beyond $0.01
returns 422 with the full math unless `force: true`.
**Guards:** 409 `baseline_already_exists` when a different baseline is
already stamped (re-running with the SAME date + balance is idempotent
and returns the existing session with `already_applied: true`);
409 `reconciliation_in_progress` when an open session exists (cancel it
first via PATCH /accounting/reconciliations/{id}).
**Posts ZERO GL.** The only GL-adjacent effect is
`journal_entry_lines.reconciled_at` flips (the same GL-neutral signal a
normal match writes). No closed-period guard applies (the anchor date
is usually historical and nothing is posted).
Supports the `Idempotency-Key` header (canonical api-v1 mutation
contract) in addition to the parameter-level idempotency above.
operationId: applyReconciliationBaselineV1
parameters:
- name: id
in: path
required: true
schema:
type: string
format: uuid
description: Bank account UUID.
requestBody:
required: true
content:
application/json:
schema:
type: object
required:
- baseline_date
- baseline_balance
properties:
baseline_date:
type: string
format: date
description: The cutover/anchor date (YYYY-MM-DD).
baseline_balance:
type: number
description: The REAL bank statement balance at the anchor date.
keep_open_gl_line_ids:
type: array
items:
type: string
format: uuid
description: >-
Journal-entry-line UUIDs to KEEP unreconciled (in-transit
checks/deposits not yet cleared at the anchor).
keep_open_bank_txn_ids:
type: array
items:
type: string
format: uuid
description: >-
Bank transaction UUIDs to KEEP unexcluded (feed lines that
must remain matchable).
force:
type: boolean
description: >-
Accept a nonzero anchor variance (default false -> 422 when
|variance| > $0.01).
notes:
type: string
nullable: true
description: Appended to the system session's notes (capped 500 chars).
responses:
'200':
description: Idempotent re-run (same date + balance already stamped)
content:
application/json:
schema:
type: object
properties:
data:
type: object
properties:
already_applied:
type: boolean
enum:
- true
baseline_date:
type: string
format: date
baseline_balance:
type: number
reconciliation:
type: object
nullable: true
'201':
description: Baseline applied
content:
application/json:
schema:
type: object
properties:
data:
type: object
properties:
reconciliation:
type: object
description: The completed system session row.
baseline_date:
type: string
format: date
baseline_balance:
type: number
gl_lines_reconciled:
type: integer
bank_transactions_excluded:
type: integer
kept_open_gl_line_count:
type: integer
kept_open_bank_txn_count:
type: integer
math:
type: object
properties:
gl_balance_at_baseline:
type: number
kept_open_total:
type: number
cleared_balance:
type: number
variance:
type: number
'400':
description: invalid_baseline_date / invalid_baseline_balance / invalid UUID
content:
application/json:
schema:
$ref: '#/components/schemas/ErrorEnvelope'
'401':
$ref: '#/components/responses/Error'
'403':
$ref: '#/components/responses/Error'
'404':
$ref: '#/components/responses/Error'
'409':
description: >-
baseline_already_exists (different params) OR
reconciliation_in_progress (cancel it first)
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
'422':
description: >-
baseline_variance_nonzero -- response body carries the full variance
math; pass force:true to accept
content:
application/json:
schema:
type: object
properties:
error:
type: string
enum:
- baseline_variance_nonzero
code:
type: string
baseline_balance:
type: number
gl_balance_at_baseline:
type: number
kept_open_total:
type: number
cleared_balance:
type: number
variance:
type: number
hint:
type: string
security:
- ApiKeyAuth: []
components:
schemas:
ErrorEnvelope:
type: object
description: |
Canonical error response envelope. All API errors use this shape.
required:
- error
- code
properties:
error:
type: string
description: Machine-readable error key
example: not_found
code:
type: string
description: Machine-readable error code (often same as error)
example: not_found
type:
type: string
enum:
- validation_error
- permission_error
- not_found
- conflict
- rate_limit
- internal
- expand_error
- not_implemented
example: not_found
hint:
type: string
description: Human-readable one-sentence explanation (English)
example: >-
The requested order does not exist or does not belong to this
entity.
param:
type: string
description: The parameter that caused the error, if applicable
example: expand[0]
required:
type: string
description: The scope required (only on insufficient_scope errors)
example: accounts:read
request_id:
type: string
description: >-
Unique request ID for support tracing (maps to CloudWatch log
stream)
example: req_abc123
Error:
description: |
Alias for ErrorEnvelope. Canonical error response shape used by all
API endpoints. Refer to ErrorEnvelope for the full field definition.
allOf:
- $ref: '#/components/schemas/ErrorEnvelope'
responses:
Error:
description: Error response (400/401/403/404/409/422/429/500)
content:
application/json:
schema:
$ref: '#/components/schemas/ErrorEnvelope'
securitySchemes:
ApiKeyAuth:
type: http
scheme: bearer
description: |
API key issued per entity via Settings > Developers > API Keys.
Each key carries scopes (e.g. orders:read, products:write).
Bearer token format: Authorization: Bearer ark_live_ent__
Test keys use ark_test_ent__. Both are issued per entity
via Settings > Developers > API Keys.
````