Line4

Solvency UK checker for your PRA returns

For UK insurers that send Solvency UK returns to the PRA. Line4 Check runs the Bank of England's own validation rules on your quarterly and annual returns, solo and group, and the annual return for third-country branches, in XBRL-XML, on the Bank's insurance taxonomy 2.2.0. Your file never leaves your computer.

Live5 Solvency UK returns on taxonomy 2.2.0: 1,173 of the Bank's 2,292 rules for these returns (51%), matched to Arelle on the Bank's own samples.

Drop your Solvency UK return here

One XBRL-XML instance (.xbrl), or a .zip holding just that file, for one of the 5 Solvency UK returns listed below, on the Bank of England's insurance taxonomy 2.2.0. Each file is checked against the Bank's rules for the return its schemaRef names.

Your file never leaves your computer. It is checked inside this browser tab: nothing is uploaded, and nothing from the file is recorded.

What we record

Your file is checked in your browser and never uploaded. This is all Line4 keeps about each check, here and on regulators’ websites that show Line4 Check.

For each check, Line4 records

  • Which return was checked and on which Bank of England taxonomy release, such as the quarterly solo return on 2.2.0
  • The file format: XBRL-XML
  • The kind of result: passed, warnings only, blocking errors, nothing could be checked, or a return not covered
  • The address of the page the check ran on, without anything after a ? or #
  • The date and time
  • Visits and clicks, counted by Vercel Web Analytics without cookies

Never recorded

  • Your file, or any part of it: it is checked in your browser and never uploaded
  • The file name
  • The entity, its LEI or the reporting date
  • Any value or message from the file, or which or how many checks failed
  • Who you are: no name, email, cookie or IP address is kept with the record

If you ask for the report by email, that report (not your file) and your email address are sent to Line4. See the privacy policy.

New to Solvency UK? Solvency UK reporting sets out who files, on which taxonomy, and by when. Filing Solvency II QRTs to a supervisor in the EU or EEA? Use the Solvency II checker, under EIOPA's rules. A check at submission is the first step to real-time supervision. Need premium support or bespoke validation? Contact us.

What Line4 Check checks

The Bank of England publishes its validation rules with each taxonomy release, as XBRL formulas in the taxonomy and in a workbook. The counts here are the rules in the XBRL for each return, less those the Bank switches off in the taxonomy package or on its deny list (last updated 3 October 2026). Each figure comes from the compiled rule files themselves.

Solo undertakings

  • Quarterly solo return (QRS)The Bank's name: Quarterly Solvency II reporting SoloRules run127of 267 · 47%Same as Arelle127 of 127on the Bank's sample
  • Annual solo return (ARS)The Bank's name: Annual Solvency II reporting SoloRules run983of 1,847 · 53%Same as Arelle983 of 983on the Bank's sample

Groups

  • Quarterly group return (QRG)The Bank's name: Quarterly Solvency II reporting GroupRules run94of 213 · 44%Same as Arelle94 of 94on the Bank's sample
  • Annual group return (ARG)The Bank's name: Annual Solvency II reporting GroupRules run213of 425 · 50%Same as Arelle213 of 213on the Bank's sample

Third-country branches

  • Annual return for third-country branches (ARB)The Bank's name: Annual Solvency II reporting Third country branchesRules run307of 696 · 44%Same as Arelle307 of 307on the Bank's sample
All 5 returnsDistinct rules: many apply to more than one return, so the rows add up to 1,724.1,173of 2,292 · 51%

There is no quarterly return for third-country branches in 2.2.0: the Bank deleted it (QRB), as PS13/26 removes third-country branches from quarterly reporting.

Every report carries the same line, for example: “This free check runs 127 of the Bank of England's 267 rules for quarterly solo returns on taxonomy 2.2.0 (47%). The Bank's filing rules are not checked yet. It is not a substitute for the validation the Bank runs when you submit.”

How we know the results are right

Every check Line4 Check runs was compared with Arelle 2.47.4, the open-source XBRL processor, on the Bank of England's own sample return for each entry point: the same result and the same number of evaluations, check by check, on 1,724 of 1,724. Then 51 facts were broken on purpose in 3 edited copies of the quarterly samples: each target check failed in Arelle and in Line4 Check, and nothing else changed.

The Bank fills its samples with random data and says they cannot be assumed to conform to its validation rules, so they fail some. On each sample, Line4 Check fails exactly the rules Arelle fails:

  • Quarterly solo return (QRS)Run on it125Passed119Failed6
  • Quarterly group return (QRG)Run on it92Passed86Failed6
  • Annual solo return (ARS)Run on it153Passed146Failed7
  • Annual group return (ARG)Run on it205Passed194Failed11
  • Annual return for third-country branches (ARB)Run on it301Passed292Failed9

The evidence is thinnest for the annual solo return: the Bank's sample fills only part of it, so 830 of the 983 annual solo checks have nothing to run on there, in Arelle or in Line4 Check. Two rules the Bank's known issues log has under review run as published, as Arelle runs them: warnings on template IR.22.01 that can fire on valid zeros (issue 198), and IR_bv1768 (issue 233), which the Bank says does not affect reporting outcomes.

Which taxonomy: 2.2.0

The Bank published the Bank of England Insurance Taxonomy 2.2.0 on 2 September 2026. The frameworks it amends and adds (DIS, IR, IMO and MAL) are effective from 1 January 2027, for reporting with a reference date on or after 31 December 2026 (Bank of England). The five returns here are the entry points of its IR framework, and a file names one in its schemaRef, such as http://www.bankofengland.co.uk/data/xbrl/md/fws/insurance/ir/2026-09-02/mod/qrs.xsd. Line4 Check matches that address exactly, so a UK file is never checked against EIOPA's rules, or an EU file against the Bank's.

How it works

  1. 01Your browser downloads the engine and the rulesThe Line4 engine with its XBRL-XML reader is compiled to WebAssembly (368 KB). Only the rules of the return you check are downloaded: the Bank’s quarterly solo rules are 53 KB, its annual solo rules 600 KB. Your browser keeps them for next time.
  2. 02Your file is opened on your computerThe XBRL-XML instance is read inside the browser tab, in a background worker so the page stays responsive. Its schemaRef says which return and taxonomy release it is. Nothing is uploaded.
  3. 03Every check runs in momentsEach failed check is listed by template, with the value found, the value expected, the Bank’s rule code and the rule in the Bank’s own words. Download it all as a CSV.

What it does not check yet

  • The Bank’s filing rulesHow the instance document itself is written, under the Bank’s XBRL Filing Manual (v1.0.1). None run yet, and every report says so.
  • The other Solvency UK returnsInternal model outputs (IMO), matching adjustment assets and liabilities (MAL), public disclosure (APS, APG), market risk sensitivities (MRS), special purpose vehicles (SPV), internal model firms (AIS) and the liquidity returns (CFL, CFS, COL, LMR). Line4 Check has not compared them with Arelle yet, so it does not run them.
  • 1,119 of the Bank’s rules for these five returns675 of them already run in Line4’s JavaScript engine, but not yet in the browser engine, so they are left out here; with them it would run 1,848 of the 2,292. The others are rules of shapes Line4 Check does not read yet. Among the rules left out is one annual rule (IR_bv0056) that Line4’s engine and Arelle read differently; the Bank’s known issues log has it under review too.
  • Rules outside the XBRLThe Bank’s workbook lists rules it does not write into the taxonomy, so there is no formula to run: 9 of the 277 for the quarterly solo return, 9 of the 223 for the quarterly group return, 122 of the 1,970 for the annual solo return, 12 of the 438 for the annual group return, 114 of the 810 for the annual third-country branch return.
  • Earlier taxonomy releasesFiles built on the Bank’s releases before 2.2.0, for reference dates before 31 December 2026.

Line4 Check is a prototype of the Line4 validation engine, not certified software. Use it to find problems early, and rely on the Bank's own validation for the result that counts.

Questions

What is Solvency UK?

The UK’s rules for insurers, which grew out of Solvency II (the PRA’s papers also say UK Solvency II). Insurance firms send their regulatory returns to the Prudential Regulation Authority (PRA), part of the Bank of England, and Solvency UK applies to all insurance regulatory reporting with reference dates of 31 December 2024 and later. Firms submit the returns through the Bank’s BEEDS portal, as XBRL built on the Bank of England Insurance Taxonomy. Bank of England · Our guide to Solvency UK reporting.

How is it different from EIOPA’s Solvency II?

Same roots, different taxonomy and rules. Insurers in the EU and EEA file on EIOPA’s taxonomy, under EIOPA’s validation rules. UK insurers file on the Bank of England Insurance Taxonomy (now 2.2.0), which uses EIOPA’s dictionary alongside the Bank’s own, with its own templates (codes starting IR, such as IR.02.01 for the balance sheet, where EIOPA’s start S), its own entry points, its own validation rules and deny list, and returns of its own, such as the matching adjustment return (MAL) that is new in 2.2.0. The Bank has told firms not to implement EIOPA’s taxonomy 2.7 or any later release. So each file needs its own publisher’s rules: Line4 Check reads the schemaRef and checks a UK file only against the Bank’s rules. The Solvency II checker.

Which returns can I check?

Quarterly solo return (QRS) (the Bank’s name: Quarterly Solvency II reporting Solo); Quarterly group return (QRG) (the Bank’s name: Quarterly Solvency II reporting Group); Annual solo return (ARS) (the Bank’s name: Annual Solvency II reporting Solo); Annual group return (ARG) (the Bank’s name: Annual Solvency II reporting Group); Annual return for third-country branches (ARB) (the Bank’s name: Annual Solvency II reporting Third country branches), all on taxonomy 2.2.0. Each is one XBRL-XML instance (.xbrl), or a .zip holding just that file. The list above gives the number of the Bank’s rules each one runs.

Is it free?

Yes. There is no account, no upload and no limit on how many returns you check. After a result you can leave your email address to get the report by email, if you want it. For premium support or bespoke validation, contact us at team@line4.ai.

Does my file leave my browser?

No. Your file never leaves your computer. Your browser downloads the Line4 engine (WebAssembly) and the Bank of England’s rules for your return from line4.ai, then opens and checks the file on your own computer. Nothing is uploaded, and nothing from the file is recorded. If you ask for the report by email, only the report you see is sent to Line4, not the file.

What does Line4 record?

For each check: the return checked and its Bank of England taxonomy release, the file format, the kind of result (passed, warnings only, blocking errors, nothing could be checked, or a return not covered), the address of the page it ran on without anything after ? or #, and the time. Never the file or any part of it, its name, the firm or its LEI, the reporting date, any value or message, or which or how many checks failed, and no name, email, cookie or IP address with the record.

Which taxonomy version does it use?

The Bank of England Insurance Taxonomy 2.2.0, published on 2 September 2026. The Bank says the frameworks it amends and adds (DIS, IR, IMO, MAL) are effective from 1 January 2027, for reporting with a reference date on or after 31 December 2026. A file names its taxonomy in its schemaRef (…/insurance/ir/2026-09-02/mod/qrs.xsd for the quarterly solo return on 2.2.0); a file built on an earlier release names another date, and Line4 Check does not check it yet. Release note.

Is this the same as the Bank’s own validation?

No. It is a free check to catch problems before you submit. The Bank runs its validation rules in its own data collection system when you submit through BEEDS, and that result is the one that counts. It can run rules Line4 Check does not, listed below.

What do errors and warnings mean?

The Bank’s validations workbook gives each rule a severity for each return: ERROR or WARNING. Line4 Check uses the same severity, return by return. Line4 Check counts failed errors as blocking and failed warnings as non-blocking.

How do you know the results are right?

Every check it runs was compared with Arelle 2.47.4, the open-source XBRL processor, on the Bank’s own sample return for each entry point: the same result and the same number of evaluations on 1,724 of 1,724 checks. Then 51 facts were broken on purpose in 3 edited copies of the quarterly samples: each target check failed in both, and nothing else changed. It is a prototype, not certified software.

Does it check the Bank’s filing rules?

Not yet. The Bank asks firms to follow its XBRL Filing Manual (v1.0.1, its release note says) for how the instance document itself is written. Line4 Check does not run those rules yet, and every report says so. EIOPA’s and EBA’s filing rules are not the Bank’s, so they are not run either.

Sources