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fix(salary): apply percent brackets for monthly incomes above 80 000 kr (#1510)

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* fix(salary): apply percent brackets for monthly incomes above 80 000 kr

Skatteverket's monthly tax tables switch from fixed krona amounts to
percent-of-income rows above 80 000 kr/month. The lookup only loaded the
krona ("30B") rows and clamped higher incomes to the last bracket,
under-withholding every salary above 80 000 kr (e.g. 100 000 kr, tabell
31 kolumn 1: 25 294 kr instead of 35 000 kr).

- fetch both 30B and 30% sections from the Skatteverket API; treat a
  missing section as API failure so the bundled fallback wins over
  incomplete data
- TaxTableRate is a discriminated union; percent brackets withhold
  percent of the whole monthly income, ore dropped per SFF 2011:1261
  22 kap. 1 (oretal bortfaller)
- fallback generator parses %-rows too; regenerated with 1 232 percent
  rows and a guard that every table carries both sections
- keep the old clamp only as a warn-logging last resort

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(salary): fail loudly on incomplete tax table data (review findings)

Address CodeRabbit and Swedish accounting review findings on #1510:

- lookupTaxAmount throws TaxTableUnavailableError when loaded brackets
  contain a gap instead of silently withholding 0
- a failed or empty pagination page fails the whole API fetch so the
  bundled fallback serves complete data
- kolumn values are parsed strictly (decimal-aware, comma accepted);
  malformed values fail the fetch instead of becoming 0 kr / 0 %
- importer rejects malformed column values instead of emitting 0
  (regenerated fallback is byte-identical)
- close the bracket gap in the calculation-engine test fixture
- clarify the ore-truncation citation and use an absolute date in
  DECISIONS.md

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(salary): validate income boundaries in tax table parsers

Round-2 CodeRabbit finding on #1510: income boundaries were still parsed
with parseInt, which accepts "100abc" and turns garbage into 0 or an
open-ended bracket. Both the importer and the API loader now require
digits-only boundaries; an empty upper bound is legal only on percent
rows (the open-ended top row). Malformed API data fails the fetch so the
bundled fallback runs; malformed TXT data fails the import. Regenerated
fallback is byte-identical.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Mattsson
2026-08-11 01:27:16 +02:00
committed by GitHub
co-authored by Claude Fable 5
parent e45218bcc6
commit 614b7e60b9
7 changed files with 8449 additions and 6889 deletions
Download Patch File Download Diff File Expand all files Collapse all files
scripts/import-tax-tables.ts
+66 -27
View File
@@ -7,19 +7,20 @@
* Output: lib/salary/tax-tables-fallback.ts
*
* Record format (49 chars per line):
* chars 0-4 (width 5): prefix : "30B29" = monthly/belopp, table 29
* chars 0-4 (width 5): prefix : "30B29" = monthly/belopp, table 29;
* "30%29" = monthly/percent, table 29
* chars 5-11 (width 7): income_from
* chars 12-18 (width 7): income_to
* chars 19-23 (width 5): column 1 tax amount (SEK)
* chars 12-18 (width 7): income_to (blank on the open-ended top %-row)
* chars 19-23 (width 5): column 1 (SEK on B-rows, percent on %-rows)
* chars 24-28 (width 5): column 2
* chars 29-33 (width 5): column 3
* chars 34-38 (width 5): column 4
* chars 39-43 (width 5): column 5
* chars 44-48 (width 5): column 6
*
* We import only B-rows (absolute amounts). %-rows (percentage-based, used for
* incomes above the highest B-row bracket) are skipped: matches the behavior
* of the Skatteverket API path which also fetches only B-rows.
* Both B-rows (absolute amounts, incomes up to 80 000 kr/month) and %-rows
* (percent of the whole income, above 80 000 kr/month) are imported. The
* emitted tuple carries an isPercent flag as its last element.
*
* Usage:
* npx tsx scripts/import-tax-tables.ts --year 2026
@@ -28,7 +29,7 @@
import { readFileSync, writeFileSync } from 'fs'
import { resolve } from 'path'
type TaxRow = readonly [number, number, number, number, number, number, number, number]
type TaxRow = readonly [number, number, number, number, number, number, number, number, number]
interface ParsedTable {
tableNumber: number
@@ -54,32 +55,54 @@ function parseLine(line: string): { table: number; row: TaxRow } | null {
if (clean.length < 49) return null
const prefix = clean.slice(0, 5)
// B-rows only (absolute amounts). Skip %-rows.
if (prefix[2] !== 'B') return null
// B-rows carry absolute SEK amounts, %-rows carry percentages for incomes
// above the highest B-row bracket. Both are needed for correct withholding.
if (prefix[2] !== 'B' && prefix[2] !== '%') return null
const isPercent = prefix[2] === '%'
const tableStr = prefix.slice(3, 5)
const table = parseInt(tableStr, 10)
if (!Number.isInteger(table)) return null
const parseField = (start: number, width: number): number => {
const raw = clean.slice(start, start + width).trim()
if (raw === '') return 0
const n = parseInt(raw, 10)
return Number.isFinite(n) ? n : 0
// Column values must be well-formed whole numbers. A malformed value falling
// back to 0 would bake 0 kr / 0 % withholding into the emitted fallback data,
// so fail the import instead.
const parseColumn = (start: number): number => {
const raw = clean.slice(start, start + 5).trim()
if (!/^\d+$/.test(raw)) {
throw new Error(`Malformed column value "${raw}" in line: ${clean}`)
}
return parseInt(raw, 10)
}
const incomeFrom = parseField(5, 7)
const incomeTo = parseField(12, 7)
const c1 = parseField(19, 5)
const c2 = parseField(24, 5)
const c3 = parseField(29, 5)
const c4 = parseField(34, 5)
const c5 = parseField(39, 5)
const c6 = parseField(44, 5)
// Income boundaries get the same digits-only rule: parseInt would accept
// "100abc" and turn other garbage into 0, silently corrupting bracket
// ranges. A blank income_to is legal only on the open-ended top %-row
// (emitted as 0, mapped to the open-ended sentinel by the loader).
const parseIncome = (start: number, allowBlank: boolean): number => {
const raw = clean.slice(start, start + 7).trim()
if (raw === '') {
if (!allowBlank) throw new Error(`Missing income boundary in line: ${clean}`)
return 0
}
if (!/^\d+$/.test(raw)) {
throw new Error(`Malformed income boundary "${raw}" in line: ${clean}`)
}
return parseInt(raw, 10)
}
const incomeFrom = parseIncome(5, false)
const incomeTo = parseIncome(12, isPercent)
const c1 = parseColumn(19)
const c2 = parseColumn(24)
const c3 = parseColumn(29)
const c4 = parseColumn(34)
const c5 = parseColumn(39)
const c6 = parseColumn(44)
return {
table,
row: [incomeFrom, incomeTo, c1, c2, c3, c4, c5, c6] as const,
row: [incomeFrom, incomeTo, c1, c2, c3, c4, c5, c6, isPercent ? 1 : 0] as const,
}
}
@@ -137,9 +160,15 @@ function emitModule(year: number, tables: ParsedTable[]): string {
* Rows: ${totalRows} across tables ${tableNumbers}
*/
/** [incomeFrom, incomeTo, col1, col2, col3, col4, col5, col6] */
/**
* [incomeFrom, incomeTo, col1, col2, col3, col4, col5, col6, isPercent]
*
* isPercent 0: columns are SEK amounts (incomes up to 80 000 kr/month).
* isPercent 1: columns are percent of the whole monthly income (above
* 80 000 kr/month). incomeTo 0 marks the open-ended top row.
*/
export type FallbackTaxRow = readonly [
number, number, number, number, number, number, number, number,
number, number, number, number, number, number, number, number, number,
]
/** Tables keyed by municipal tax rate number (29-42). */
@@ -166,11 +195,21 @@ function main() {
const tables = parseFile(inputPath)
if (tables.length === 0) {
throw new Error('No B-rows parsed: check input file format')
throw new Error('No rows parsed: check input file format')
}
// Every table must have both sections: a B-only table would clamp high
// incomes to the last krona bracket and silently under-withhold.
for (const t of tables) {
const percentRows = t.rows.filter(r => r[8] === 1).length
if (percentRows === 0 || percentRows === t.rows.length) {
throw new Error(`Table ${t.tableNumber}: expected both B-rows and %-rows, got ${percentRows}/${t.rows.length} percent rows`)
}
}
const totalRows = tables.reduce((sum, t) => sum + t.rows.length, 0)
console.log(`Parsed ${tables.length} tables (${tables.map(t => t.tableNumber).join(', ')}), ${totalRows} B-rows total`)
const percentTotal = tables.reduce((sum, t) => sum + t.rows.filter(r => r[8] === 1).length, 0)
console.log(`Parsed ${tables.length} tables (${tables.map(t => t.tableNumber).join(', ')}), ${totalRows} rows total (${percentTotal} percent rows)`)
const moduleSource = emitModule(year, tables)
writeFileSync(outputPath, moduleSource, 'utf-8')