One payment had to name one document and could take no discount or
processor fee, so paying several invoices from one deposit meant several
entries and the fee had nowhere to go. This adds the kernel's exact
settlement arithmetic (applications total, net deposit), a Ledger::settle
that posts one entry for a customer's or vendor's documents, and the gross
method and gross fee A-8/A-4 chose.
- kernel::settle: sum(cash)+sum(discounts)=applications, sum(cash)-fee=
deposit, None on overflow or a negative deposit. Kani settle_is_exact
plus the Decimal bridge.
- Ledger::settle / settlement_lines: one party and one kind per
settlement, one application per document, each cash+discount within
payment_room; a discount within the terms (discount_max and
discount_by) needs no reason, a larger or later one does; a bill with
an asset line is refused with D-49's remedy; a fee is a customer
payment's only and posts gross.
- Rows are payment lines in application order, then discount lines, the
fee line and the cash line, so a journaled event's line indices are
stable; replay tags exactly the line an event names and leaves an
unmatched line unattached (never refuses).
- receive_payment_with and pay_bill_with become one-application calls.
- Roles: sales_allowances (4100), purchase_discounts (6995) and
payment_processing_fees (6060), constants used on demand but not added
to control_accounts() (existing charts may use those codes for other
things).
- Lean: settle posts through Step.document, so settle_posts_a_document_step
and settle_unattached, no new constructor; both in Audit.lean.
- Core tests: bill_on_terms_with_discount, late_discount_needs_a_reason,
discount_on_an_asset_bill_is_refused_with_the_remedy,
a_fee_posts_gross_to_receivables_and_net_to_the_bank,
a_settlement_names_its_lines_and_refuses_a_document_twice, and
equipment_bill_payment_is_investing_cash in the cash-flow suite.
- Bookspec B-42 is stated, with its id BS-arap-6; the catalogue and index
now record it as CONVENTION.
just check and just prove green.
Documents could name only one revenue or general-expenses account per
project, had no number of their own, and took a due date the caller had
to work out. This slice gives the core the pieces the rest of S4 needs,
and journals nothing: an old-shape document still writes byte for byte,
so the owner's books need no upgrade for it.
- Payment terms (B-39): Net n, Net n EOM, due on receipt and a custom
date, with the early-payment discount and its exact bound
(kernel::discount_max, Kani + bridge). A due date past the calendar's
end is refused, never a panic, and a discount is refused with terms
that have no net days.
- Invoice numbers (B-40, A-2): first_number plus the count of numbered
invoices, zero-padded to four digits and wider past 9,999, stored at
issue, kept by a void; legacy invoices are uncounted.
- Line accounts (A-10): a document line may name its account, and the
entry posts one line per (account, project) part. An invoice line takes
revenue or a liability holding no role (deferred revenue); a bill line
an expense or a non-cash asset holding no role. Roles, cash accounts
and headers are refused.
- A line's amount is exactly its quantity times its unit price
(kernel::line_amount, Kani + bridge): both or neither, never rounded.
- A vendor's invoice number names one standing bill per vendor, with
case, spaces and hyphens ignored, unless a duplicate reason says why
(B-40).
- The record fields S4.3 will journal: number, terms, bill-to and seller
snapshots, customer reference, memo, the empty sends list S5 fills, and
the bill's received_on, all optional and defaulted.
The store refuses a line carrying an account, quantity or unit price
before it rehearses or journals anything: those fields are journaled from
S4.3's documents_v2 on, and I-3 will not let a public write replay
without them. `document_line_fields_wait_for_documents_v2` proves the
refusal, the unchanged journal and allocators, and that an ordinary line
journals exactly as before. S4.3 removes this guard in the same change
that journals the fields and adds its byte-for-byte test.
The document commands keep their signatures; create_invoice_with and
create_bill_with take the optional fields for S4.3 and for tests. They
are the existing issue commands with more fields, not a new state
transition, so no Lean Step is added. Kani: line_amount_is_exact runs in
`just prove`; discount_max_is_bounded relates a product to a quotient and
runs in `prove-slow` (163 s), as the proration charge harnesses do.
just check green; just prove green.
Book value is cost less what the books posted; the schedule's figure is
apart. An asset's acquired date comes from its entry. Contributed
property keeps its section 723 carryover basis apart from its depreciable
basis (the lower of value and adjusted basis), with its 704(c) built-in
gain and method. The K-1 worksheet reports tax-basis capital (Form 1065
Item L) beside the book figures, leaving open what only the CPA knows.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj
The final month takes what the months before leave, spread over its days;
a disposed asset stops on its disposal day. A skipped month is caught up
in the month the run is made; a reversed run un-posts its month. New
schedules spread by day; equal-months schedules must start on the 1st.
Amounts round to the currency's own minor unit. Kani and Lean proofs; an
exhaustive search over runs, reversals and disposals.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj
A vendor's 1099 decision is its own dated fact (files NEC or MISC, not
reportable with its reason, or undetermined), applied by each payment's
date. Payment methods are recorded; card and network payments are left
out and listed; a member's check through financing counts; a bank payment
with no method counts (D-40); $2,000 for payments after 2025. One
worksheet for the tool, the viewer and the CPA package.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj
Each party's part of an entry is signed as its own account would show it,
with a direction and its cash and in-kind amounts; a reversal is its
original negated. Totals on a cash or all basis: for a member, all equals
the members' equity statement and cash the K-1's cash. Money is cash,
cards and the financing accounts, and a liability credit never pays its
own creditor (creditor_of), so accruals and declared distributions count
once. tin_last4 from the TIN or W-9 facts.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj
Direct method with the operating reconciliation and noncash schedules; it
foots by construction (Lean and Kani). Every non-cash account belongs to
one section; reversals net; a member or lender paying for the company is
cash borrowed and spent (D-42, constructive receipt and disbursement);
property a member contributes stays noncash. The bookspec seed: one loader
checks every example.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj
Members' shares of earnings are split cumulatively by largest remainder in
the closes, the members' equity statement, the K-1 worksheet and the
viewer, so a member's capital on a given day never moves by a cent when its
month is later closed. Old closes replay as they were; the first P3 close
carries any true-up. Feature members_cumulative. Kani and Lean proofs of
the bounded drift; bookspec examples.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj
Max-testing pass, step 2: two spec decisions the owner confirmed
(2026-10-13), each test-first.
Aging (arap::aging_bucket): a document due today was "1-30 days past
due"; it is Current, since past due starts the day after (QuickBooks'
convention). Spec in the doc comment. Boundary examples at every edge
(due today, 1, 30, 31, 60, 61, 90, 91 days) fail on the old code. A
property: the balance lands in exactly one bucket, and time only ages
it.
Member splits (periods::allocate): the last member absorbed every odd
cent, so the same partner always got or lost it. Now largest remainder:
each share rounded toward zero to the cent, leftover cents to the
largest remainders, ties to the earlier member, a loss the negation of
the gain. The core is a new kernel function, kernel::apportion,
allocation-free so Kani proves it (n <= 3): apportion_is_exact (it
succeeds exactly when the shortfall is under a unit per part; then the
parts sum to the whole, each gains 0 or 1 unit, one may take the
sub-unit fraction) and apportion_is_fair (never a unit to a part while
a larger remainder goes without). Kani found an off-by-one in the first
version: a shortfall of n units plus a fraction was accepted. Native
regression apportion_refuses_a_shortfall_of_a_unit_per_part_or_more.
Properties at Decimal (2,000 cases, up to 5 members): conservation,
within a cent of each exact share, fairness, sign symmetry; they fail on
the old rule. Bridge: apportion agrees on i64 and Decimal.
Contract: closes journaled before this change replay exactly. New
member closes journal "rounding": "largest_remainder"; journal lines
without it replay as CloseTo::MembersLastAbsorbs, the old rule
(periods::allocate_last_absorbs, pinned by
closes_journaled_under_the_old_rule_replay_with_it). The members'
equity statement isn't journaled and uses the new rule.
Open gap: Lean proof of apportion's sum law for any n (needs a
permutation lemma on the ranking); Kani covers n <= 3, properties n <= 5.
The Lean closing theorems already hold for any split summing to the
net.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX
The money arithmetic every invariant rests on now lives in one kernel,
ledger-core/src/kernel.rs: signing a line, totals, net, per-account
movements, reversal, normal balances, trial-balance columns, closing
lines, and the rounding plug for member splits. It is generic over a
checked `Amount` trait. The engine runs it on Decimal (validate,
movements, reverse_entry, account_balance, close_period_to, allocate,
trial_balance): there is one copy of the arithmetic, and it is the one
under proof.
Three layers, docs/verification.md maps every law to its proofs:
- Kani (src/proofs.rs): 17 harnesses prove the kernel at i64 for every
input up to 4 lines over 3 accounts. An entry is accepted exactly
when it is two or more positive, in-range lines whose debits equal
credits; accepted entries net to zero; grouping by account loses
nothing; a reversal mirrors and cancels its original; trial-balance
columns balance iff the books net to zero; closing lines zero their
accounts and a close balances however the net is split; the plug
makes parts sum to the whole. No panics, no overflow. kani::cover!
shows the proofs are not vacuous.
- Lean 4 (verify/lean): 24 headline theorems for books of any size. The
ledger is a state machine (add account, draft, post, reverse, open,
close), and in every reachable state the books net to zero, the trial
balance balances (as of any date), and the accounting equation holds.
Posting only appends ("posted is forever"), closed periods are
frozen, a close zeroes revenue and expenses and credits exactly the net
income, and period statements add up. Audit.lean shows standard axioms
only, no sorry.
- Bridge (tests/kernel_bridge.rs): the Decimal and i64 kernels agree.
What the proofs found (each one missed by every test, fuzzer, and
mutant):
- The engine accepted negative line amounts; only MCP refused them. Now
NegativeAmountLine: direction is the side's job.
- Summing lines near Decimal::MAX panicked. Lines are now capped at one
quadrillion and ten decimal places (AmountOutOfRange), which keeps
every realistic sum exact, and the kernel's sums are checked.
- FX conversion (foreign_amount * fx_rate) could panic the same way; it
is now a checked multiply.
- Kani itself: 0.68 mis-models symbolic-length copy_from_slice
(model-checking/kani#4904) and reported a reversal that doesn't net to
zero. The counterexample, replayed natively, passes, and a 15-line
standalone crate reproduces the bug. Harnesses avoid bulk copies, and
a should_panic canary will flag the upstream fix.
`just prove` runs it all (Kani memory- and time-capped, fails on an
unsatisfiable cover or a non-standard Lean axiom). AGENTS.md now makes
formal coverage part of every core change.
Also, docs: GnuCash is *an* oracle, never *the* oracle (the owner). The
spec is accounting principles, proved. Golden files are recomputed from
principles. External implementations (GnuCash, the old Sheet, QBO/Xero)
are cross-checks whose disagreements get adjudicated, never obeyed.
docs/oracle.md gains "Who is right"; AGENTS, README, architecture,
roadmap, parity, and STATUS are reworded to match.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX
swaits
