feat(package): aging CSVs in the export and the CPA package (P4b S6)

The CPA's first tie-out is that the aging equals the control account, so
books.export and the CPA package now write ar_aging.csv and ap_aging.csv
from one builder: one row per open document (number, party, dates, terms,
total, paid, discounted, outstanding, bucket, days overdue) and a TOTAL
line carrying the outstanding sum, the GL account and balance, and the
difference (always 0.00; B-23, B-38 INVARIANT 1). XLSX and PDF lay the
same aging out as a statement with the tie-out beneath it.

The package README states the tie-out, the gross discount method (A-8)
and the direct write-off method (A-5). The chart templates gain 6995
Purchase Discounts so no template puts another account at a control
role's code (4100 and 6060 already match). The viewer's Money out list
gains the discount-deadline column and colours a due-soon or
discount-open date; the screenshot is re-rendered.

Test: the_aging_csvs_tie_to_the_control_check in ledger-package; the
existing package file-order test and mcp_journeys see the two new files.

crates/ledger-gui/src/pages/invoices.rs

@@ -55,6 +55,7 @@ struct Item {
     party: String,
     date: NaiveDate,
     due: NaiveDate,
+    terms: Option<ledger_core::Terms>,
     state: Result<Option<DocState>, ledger_core::LedgerError>,
 }
 
@@ -74,6 +75,7 @@ fn items(b: &Books, bills: bool) -> Vec<Item> {
                     .unwrap_or_default(),
                 date: d.date,
                 due: d.due_date,
+                terms: d.terms.clone(),
                 state: b.doc_today(DocRef::Bill(d.id)),
             })
             .collect()
@@ -89,6 +91,7 @@ fn items(b: &Books, bills: bool) -> Vec<Item> {
                     .unwrap_or_default(),
                 date: d.date,
                 due: d.due_date,
+                terms: d.terms.clone(),
                 state: b.doc_today(DocRef::Invoice(d.id)),
             })
             .collect()
@@ -282,26 +285,23 @@ pub fn show_list(ui: &mut Ui, b: &Books, bills: bool, shell: &mut Shell<'_>) {
                 return;
             }
             let amt = widgets::AMOUNT_MIN + 16.0;
-            let fixed = 110.0 + 104.0 * 2.0 + 120.0 + amt * 2.0;
+            let fixed = 110.0 + 104.0 * 2.0 + 120.0 + amt * 2.0 + if bills { 104.0 } else { 0.0 };
             let w = ui.available_width().max(fixed + 160.0);
             widgets::min_width(ui, "invoice_list", w, |ui| {
                 let head = |t: &str, cw: f32, right: bool| (t.to_string(), cw, right, p.muted);
-                row(
-                    ui,
-                    w,
-                    &[
-                        head("Document", 110.0, false),
-                        head(if bills { "Vendor" } else { "Customer" }, 0.0, false),
-                        head("Date", 104.0, false),
-                        head("Due", 104.0, false),
-                        head("Status", 120.0, false),
-                        head("Total", amt, true),
-                        head("Still owed", amt, true),
-                    ],
-                    None,
-                    true,
-                    false,
-                );
+                let mut header = vec![
+                    head("Document", 110.0, false),
+                    head(if bills { "Vendor" } else { "Customer" }, 0.0, false),
+                    head("Date", 104.0, false),
+                    head("Due", 104.0, false),
+                    head("Status", 120.0, false),
+                    head("Total", amt, true),
+                    head("Still owed", amt, true),
+                ];
+                if bills {
+                    header.push(head("Discount by", 104.0, false));
+                }
+                row(ui, w, &header, None, true, false);
                 widgets::rule(ui);
                 for it in rows {
                     let (status, total, owed, late) = match &it.state {
@@ -314,28 +314,49 @@ pub fn show_list(ui: &mut Ui, b: &Books, bills: bool, shell: &mut Shell<'_>) {
                         Ok(None) => ("Unknown".into(), String::new(), String::new(), false),
                         Err(_) => ("Can't compute".into(), String::new(), String::new(), false),
                     };
+                    let discount_by = it.terms.as_ref().and_then(|t| t.discount_by(it.date));
+                    let discount_open = bills && discount_by.is_some_and(|d| d >= b.today);
+                    let discount_soon = discount_open
+                        && discount_by.is_some_and(|d| d <= b.today + chrono::Days::new(3));
+                    let due_soon = bills
+                        && matches!(&it.state, Ok(Some(s))
+                            if !s.outstanding.is_zero() && s.status != DocStatus::Void)
+                        && it.due <= b.today + chrono::Days::new(7);
                     let name = format!("{}, {}, {}, owes {}", it.name, it.party, status, owed);
-                    let resp = row(
-                        ui,
-                        w,
-                        &[
-                            (it.name.clone(), 110.0, false, p.text),
-                            (it.party.clone(), 0.0, false, p.text),
-                            (fmt::date(it.date), 104.0, false, p.text),
-                            (
-                                fmt::date(it.due),
-                                104.0,
-                                false,
-                                if late { p.warning } else { p.text },
-                            ),
-                            (status, 120.0, false, if late { p.warning } else { p.muted }),
-                            (total, amt, true, p.text),
-                            (owed, amt, true, p.text),
-                        ],
-                        None,
-                        false,
-                        true,
-                    );
+                    let mut cells = vec![
+                        (it.name.clone(), 110.0, false, p.text),
+                        (it.party.clone(), 0.0, false, p.text),
+                        (fmt::date(it.date), 104.0, false, p.text),
+                        (
+                            fmt::date(it.due),
+                            104.0,
+                            false,
+                            if late || due_soon { p.warning } else { p.text },
+                        ),
+                        (
+                            status.clone(),
+                            120.0,
+                            false,
+                            if late { p.warning } else { p.muted },
+                        ),
+                        (total, amt, true, p.text),
+                        (owed, amt, true, p.text),
+                    ];
+                    if bills {
+                        cells.push((
+                            discount_by.map(fmt::date).unwrap_or_default(),
+                            104.0,
+                            false,
+                            if discount_soon {
+                                p.warning
+                            } else if discount_open {
+                                p.text
+                            } else {
+                                p.muted
+                            },
+                        ));
+                    }
+                    let resp = row(ui, w, &cells, None, false, true);
                     // Named in full, for assistive tech (and the tests).
                     resp.widget_info(|| {
                         egui::WidgetInfo::labeled(egui::WidgetType::Button, true, &name)

crates/ledger-gui/tests/invoices.rs

@@ -156,6 +156,8 @@ fn the_list_shows_the_ledgers_figures() {
     );
     let mut h = open(&dir, Route::Payables);
     shot(&mut h, "payables");
+    // The Money out list carries the discount-deadline column (blank
+    // until terms are journaled, S4.3).
     assert!(
         h.query_by_label_contains("Bill 1, Clay Co, Open, owes 300.00")
             .is_some()

crates/ledger-import/src/templates.rs

@@ -307,6 +307,12 @@ pub fn chart_template(entity: EntityType, owners: &[String]) -> Result<ChartTemp
             "expense",
             Some("nondeductible"),
         ),
+        acct(
+            "6995",
+            "Purchase Discounts",
+            "expense",
+            Some("other_deductions"),
+        ),
         acct(
             "7100",
             "Employee Benefits",

crates/ledger-package/src/aging.rs

@@ -0,0 +1,216 @@
+//! The receivables and payables agings as files (plan P4b S6, 8.3.10;
+//! rules.md B-18, B-23): one row per open document, and a tie-out line
+//! against the control account. The server's `books.export` and the CPA
+//! package build the same CSV from this, and its XLSX/PDF from
+//! [`aging_statement`], so a CPA's two copies can't differ.
+
+use ledger_core::{DocRef, Ledger};
+use rust_decimal::Decimal;
+
+use crate::text::{csv_escape, money};
+
+/// The CSV's header: one row per open document (8.3.10).
+pub const AGING_CSV_HEADER: &str =
+    "number,party,date,due_date,terms,total,paid,discounted,outstanding,bucket,days_overdue";
+
+/// One aging's rows and tie-out as CSV: the header, one row per open
+/// invoice (`invoices` true) or bill, then `TOTAL,,,,,,,,<Σ
+/// outstanding>,GL <account> <balance>,difference <difference>`.
+pub fn aging_csv(
+    ledger: &Ledger,
+    invoices: bool,
+    as_of: chrono::NaiveDate,
+) -> Result<String, String> {
+    let docs = ledger
+        .aging_documents(as_of, invoices)
+        .map_err(|e| e.to_string())?;
+    let mut out = String::from(AGING_CSV_HEADER);
+    out.push('\n');
+    let mut total = Decimal::ZERO;
+    for d in &docs {
+        total += d.outstanding;
+        out.push_str(&format!(
+            "{},{},{},{},{},{},{},{},{},{},{}\n",
+            csv_escape(&number(ledger, d.doc)),
+            csv_escape(&d.party),
+            d.date,
+            d.due_date,
+            csv_escape(d.terms.as_deref().unwrap_or("")),
+            money(d.total),
+            money(d.paid),
+            money(d.discounted),
+            money(d.outstanding),
+            d.bucket,
+            d.days_overdue,
+        ));
+    }
+    let (code, balance, difference) = tie_out(ledger, invoices, as_of)?;
+    let account = if code.is_empty() {
+        "GL —".to_string()
+    } else {
+        format!("GL {code}")
+    };
+    out.push_str(&format!(
+        "TOTAL,,,,,,,,{total},{account} {balance},difference {difference}\n",
+        total = money(total),
+        balance = money(balance),
+        difference = money(difference),
+    ));
+    Ok(out)
+}
+
+/// The same aging as a laid-out statement for XLSX and PDF: one line per
+/// party with its six bucket amounts, the totals, and the tie-out.
+pub fn aging_statement(
+    ledger: &Ledger,
+    invoices: bool,
+    as_of: chrono::NaiveDate,
+) -> Result<ledger_import::Statement, String> {
+    use ledger_import::report::{Row, RowKind, Statement};
+    let party_rows = if invoices {
+        ledger.ar_aging(as_of)
+    } else {
+        ledger.ap_aging(as_of)
+    }
+    .map_err(|e| e.to_string())?;
+    let (code, balance, difference) = tie_out(ledger, invoices, as_of)?;
+    let columns: Vec<String> = ["Current", "1-30", "31-60", "61-90", "90+", "Total"]
+        .into_iter()
+        .map(str::to_string)
+        .collect();
+    let mut out_rows: Vec<Row> = vec![Row {
+        kind: RowKind::Section,
+        label: if invoices {
+            "Receivables".into()
+        } else {
+            "Payables".into()
+        },
+        amounts: vec![],
+        currency: false,
+        rule_above: false,
+    }];
+    let (mut current, mut d30, mut d60, mut d90, mut d90p) = (
+        Decimal::ZERO,
+        Decimal::ZERO,
+        Decimal::ZERO,
+        Decimal::ZERO,
+        Decimal::ZERO,
+    );
+    for r in &party_rows {
+        let total = r.total().map_err(|e| e.to_string())?;
+        current += r.current;
+        d30 += r.days_30;
+        d60 += r.days_60;
+        d90 += r.days_90;
+        d90p += r.days_90_plus;
+        out_rows.push(Row {
+            kind: RowKind::Line,
+            label: r.name.clone(),
+            amounts: vec![
+                Some(r.current),
+                Some(r.days_30),
+                Some(r.days_60),
+                Some(r.days_90),
+                Some(r.days_90_plus),
+                Some(total),
+            ],
+            currency: false,
+            rule_above: false,
+        });
+    }
+    let total = current + d30 + d60 + d90 + d90p;
+    out_rows.push(Row {
+        kind: RowKind::Total,
+        label: "Total".into(),
+        amounts: vec![
+            Some(current),
+            Some(d30),
+            Some(d60),
+            Some(d90),
+            Some(d90p),
+            Some(total),
+        ],
+        currency: true,
+        rule_above: true,
+    });
+    out_rows.push(Row {
+        kind: RowKind::Spacer,
+        label: String::new(),
+        amounts: vec![],
+        currency: false,
+        rule_above: false,
+    });
+    out_rows.push(Row {
+        kind: RowKind::Section,
+        label: "Tie-out".into(),
+        amounts: vec![],
+        currency: false,
+        rule_above: false,
+    });
+    out_rows.push(Row {
+        kind: RowKind::Line,
+        label: if code.is_empty() {
+            "GL balance".to_string()
+        } else {
+            format!("GL {code} balance")
+        },
+        amounts: vec![None, None, None, None, None, Some(balance)],
+        currency: false,
+        rule_above: false,
+    });
+    out_rows.push(Row {
+        kind: RowKind::Total,
+        label: "Difference".into(),
+        amounts: vec![None, None, None, None, None, Some(difference)],
+        currency: true,
+        rule_above: true,
+    });
+    Ok(Statement {
+        // Excel sheet names take no slash; the statement's title is the
+        // one both XLSX and PDF draw.
+        title: if invoices {
+            "AR Aging".into()
+        } else {
+            "AP Aging".into()
+        },
+        period: format!("As of {}", as_of.format("%B %-d, %Y")),
+        columns,
+        rows: out_rows,
+        percent_from: None,
+    })
+}
+
+/// The document's number for the aging's first column: an invoice's issued
+/// number, a bill's vendor number, else the document's own name.
+fn number(ledger: &Ledger, doc: DocRef) -> String {
+    match doc {
+        DocRef::Invoice(id) => ledger
+            .get_invoice(id)
+            .and_then(|i| i.number.clone())
+            .unwrap_or_else(|| format!("Invoice {id}")),
+        DocRef::Bill(id) => ledger
+            .get_bill(id)
+            .and_then(|b| b.vendor_ref.clone())
+            .unwrap_or_else(|| format!("Bill {id}")),
+    }
+}
+
+/// The control account's code, balance and difference as of the day
+/// ([`Ledger::control_check`]): the aging's tie-out.
+fn tie_out(
+    ledger: &Ledger,
+    invoices: bool,
+    as_of: chrono::NaiveDate,
+) -> Result<(String, Decimal, Decimal), String> {
+    let role = if invoices { "receivables" } else { "payables" };
+    let checks = ledger.control_check(as_of).map_err(|e| e.to_string())?;
+    let Some(check) = checks.iter().find(|c| c.role == role) else {
+        return Ok((String::new(), Decimal::ZERO, Decimal::ZERO));
+    };
+    let code = ledger
+        .chart()
+        .get(check.account)
+        .map(|a| a.code.clone())
+        .unwrap_or_default();
+    Ok((code, check.balance, check.difference))
+}

crates/ledger-package/src/lib.rs

@@ -23,6 +23,7 @@
 //!      whichever [`PackageBooks`] they are read through.
 //! ```
 
+mod aging;
 mod attention;
 mod books;
 mod iif;
@@ -34,6 +35,7 @@ mod text;
 mod tins;
 mod vendor_1099;
 
+pub use aging::{AGING_CSV_HEADER, aging_csv, aging_statement};
 pub use attention::{
     Attention, Integrity, Report, Severity, Target, files_1099, find, find_with, reconcile_prompt,
     w9_missing, w9_prompt,

crates/ledger-package/src/package.rs

@@ -372,6 +372,17 @@ pub fn build_package<B: PackageBooks + ?Sized>(
         files.push((format!("{name}.pdf"), pdf(st)?));
         files.push((format!("{name}.xlsx"), xlsx(XlsxReport::Statement(st))?));
     }
+    // The receivables and payables agings, each with its tie-out line to
+    // the control account (B-23, 8.3.10): the same CSV books.export and
+    // the viewer make.
+    files.push((
+        "ar_aging.csv".into(),
+        crate::aging::aging_csv(ledger, true, as_of)?.into_bytes(),
+    ));
+    files.push((
+        "ap_aging.csv".into(),
+        crate::aging::aging_csv(ledger, false, as_of)?.into_bytes(),
+    ));
     // The fixed asset register, when an asset was acquired by as_of (one
     // acquired later is not in it, so neither is an empty register).
     if ledger
@@ -566,7 +577,7 @@ pub fn build_package<B: PackageBooks + ?Sized>(
     let year_end = NaiveDate::from_ymd_opt(year, 12, 31) == Some(as_of);
     let include_tins = tins.is_some();
     let readme = format!(
-        "{name} — books package for the CPA\n\nFiscal year to date: {fy_start} through {as_of_s}. {basis} basis.\nKept in wanderbooks: double-entry books from an append-only, hash-chained journal ({seq} events, verified).\n\nStatements (PDF and XLSX): profit and loss, balance sheet, cash flow, {members}tax summary, trial balance.\nLedgers (XLSX): general ledger by account; general journal entry by entry.\n{iif}{worksheet}{k1}{receipts}{tins}\nThe tax summary maps accounts to return categories; it's a worksheet, not a filing. Questions go to the owners, who can ask their bookkeeping agent to trace any number to its entries and receipts.\n",
+        "{name} — books package for the CPA\n\nFiscal year to date: {fy_start} through {as_of_s}. {basis} basis.\nKept in wanderbooks: double-entry books from an append-only, hash-chained journal ({seq} events, verified).\n\nStatements (PDF and XLSX): profit and loss, balance sheet, cash flow, {members}tax summary, trial balance.\nLedgers (XLSX): general ledger by account; general journal entry by entry.\nAgings (CSV): ar_aging.csv and ap_aging.csv, one row per open invoice or bill, each ending with a TOTAL line that ties to its control account (B-23). Early-payment discounts are taken by the gross method (A-8); bad debts are written off directly (A-5).\n{iif}{worksheet}{k1}{receipts}{tins}\nThe tax summary maps accounts to return categories; it's a worksheet, not a filing. Questions go to the owners, who can ask their bookkeeping agent to trace any number to its entries and receipts.\n",
         name = company.name,
         basis = company.basis,
         members = if company.members.is_empty() {

crates/ledger-package/tests/package.rs

@@ -338,6 +338,8 @@ fn a_single_member_package_holds_the_documented_files_in_order() {
         "tax-summary.xlsx".into(),
         "trial-balance.pdf".into(),
         "trial-balance.xlsx".into(),
+        "ar_aging.csv".into(),
+        "ap_aging.csv".into(),
         "general-ledger.xlsx".into(),
         "general-journal.xlsx".into(),
         "1099-worksheet-2026.csv".into(),
@@ -2446,3 +2448,82 @@ fn the_k1_worksheet_reports_tax_basis_capital() {
     // The book worksheet is the same as without assets' bases.
     assert!(text(&p, "k1-members.csv").contains(",1685.00\n"));
 }
+
+/// The CPA package's aging CSVs are the agings, one row per open document
+/// and a tie-out line that equals the control account (plan P4b S6,
+/// 8.3.10; rules.md B-23, B-38 INVARIANT 1).
+#[test]
+fn the_aging_csvs_tie_to_the_control_check() {
+    let dir = tempfile::Builder::new()
+        .prefix("wb-package-aging-")
+        .tempdir()
+        .unwrap();
+    let mut s = Store::create(&dir.path().join("books-data"), Currency::USD).unwrap();
+    for (code, name, ty) in [
+        ("1000", "Checking", AccountType::Asset),
+        ("3000", "Capital", AccountType::Equity),
+    ] {
+        s.add_account(code, name, ty, None, false).unwrap();
+    }
+    let bank = id_of(&s, "1000");
+    let customer = s.add_customer("Fernhill Labs").unwrap();
+    let vendor = s.add_vendor("Tobin Harlow Supply").unwrap();
+    let line = |what: &str, cents: i64| DocumentLine {
+        description: what.into(),
+        amount: Decimal::new(cents, 2),
+        class_id: None,
+        account: None,
+        quantity: None,
+        unit_price: None,
+    };
+    let invoice = s
+        .create_invoice(
+            customer,
+            d("2026-02-01"),
+            d("2026-03-01"),
+            vec![line("Consulting", 50_000)],
+        )
+        .unwrap();
+    let bill = s
+        .create_bill(
+            vendor,
+            d("2026-02-02"),
+            d("2026-03-04"),
+            vec![line("Paper", 20_000)],
+        )
+        .unwrap();
+    s.receive_payment(invoice, d("2026-02-10"), Decimal::new(20_000, 2), bank)
+        .unwrap();
+    s.pay_bill(bill, d("2026-02-11"), Decimal::new(10_000, 2), bank)
+        .unwrap();
+    let p = build_package(
+        &s,
+        &settings(&company(false), &cash()),
+        &request(false, None),
+    )
+    .unwrap();
+    for (name, role, code, balance) in [
+        ("ar_aging.csv", "receivables", "1200", "300.00"),
+        ("ap_aging.csv", "payables", "2000", "100.00"),
+    ] {
+        let csv = text(&p, name);
+        let total = csv.lines().last().unwrap();
+        assert!(
+            total.starts_with("TOTAL,,,,,,,,300.00") || total.starts_with("TOTAL,,,,,,,,100.00")
+        );
+        assert!(
+            total.contains(&format!("GL {code} {balance}")),
+            "{name}: {total}"
+        );
+        assert!(total.ends_with("difference 0.00"), "{name}: {total}");
+        let check = s
+            .ledger()
+            .control_check(d("2026-12-31"))
+            .unwrap()
+            .into_iter()
+            .find(|c| c.role == role)
+            .unwrap();
+        assert_eq!(check.balance.to_string(), balance, "{name}");
+        assert_eq!(check.difference, Decimal::ZERO, "{name}");
+    }
+}