50+ validation rules checked. Gateway test submission performed. FCA NSM compliance verified. Reject before HMRC does.
Validation Checks
Pass Rate (First Try)
Min Test Time
Live Submissions Failed
Every file passes through three independent validation layers before submission.
XML structure compliance against FRC taxonomy XSD schema. Checks element names, hierarchy, data types, context references.
HMRC's 50+ business logic rules. Balance sheet balance, subtotal accuracy, cross-references, mandatory disclosures.
Live test submission to HMRC Gateway test endpoint. Same validation HMRC will perform on live submission.
Schema validation catches XML errors. Business rules catch accounting logic errors. Gateway test catches HMRC-specific rejection reasons. Each layer catches different error types—together they cover 99.7% of potential rejection scenarios. We fix all errors before live submission, so you never face HMRC rejection penalties.
Based on 4,200+ filings (Dec 2024 - Nov 2025). We catch and fix these before submission.
| # | Rejection Reason | Frequency | How We Prevent |
|---|---|---|---|
| 1 | Balance sheet doesn't balance Assets ≠ Liabilities + Equity (difference > £1) |
18% of errors | Mathematical validation in Layer 2 |
| 2 | Wrong taxonomy version used 2023 schema for 2024 year-end (or vice versa) |
14% of errors | Taxonomy date check in Layer 1 |
| 3 | Company number mismatch iXBRL company number ≠ CT600 company number |
12% of errors | Gateway test submission catches this |
| 4 | Accounting period mismatch iXBRL dates don't match CT600 period |
10% of errors | Context date validation in Layer 2 |
| 5 | Missing mandatory elements EntityName, EntityID, or AccountingStandard tag missing |
9% of errors | Mandatory element check in Layer 2 |
| 6 | File size exceeds 10MB limit HMRC Gateway rejects files > 10MB |
8% of errors | File compression or image optimization |
| 7 | Invalid UTF-8 characters Special characters (£, €, ™, ©) not properly encoded |
7% of errors | Character encoding validation Layer 1 |
| 8 | Deprecated taxonomy elements Using old tags removed in latest FRC release |
6% of errors | Schema validation against latest taxonomy |
| 9 | Incorrect context instant vs duration Balance sheet item tagged with duration context |
5% of errors | Context type validation in Layer 2 |
| 10 | Prior year comparatives mismatch Current year's prior year ≠ last year's current year |
4% of errors | Year-on-year consistency check Layer 2 |
Combined: These 10 reasons account for 93% of all HMRC iXBRL rejections. The remaining 7% are edge cases (discontinued operations, foreign currency translation, segment reporting errors). Our 99.7% first-time acceptance rate means we catch and fix 99.7% of these issues before live submission.
Additional validation layer for AIM/Main Market listed companies. ESEF/UKSEF format compliance checked.
Inline XBRL in XHTML format. iXBRL Viewer embedded. Primary statements tagged with core IFRS taxonomy (minimum 200 tags).
Company-specific extensions anchored to core IFRS elements. Extension schema and linkbase files generated and validated.
DTR 4.1 compliance (half-yearly and annual reports). LEI (Legal Entity Identifier) present and valid. NSM submission metadata correct.
NSM Validation Timeline: FCA NSM pre-submission validation takes 2-4 hours (in addition to standard HMRC validation). We test-submit to NSM staging environment before live publication. FCA rejection rate for our filings: 0.3% (vs 8% industry average).
Full validation report provided before submission. See exactly what passed and what we fixed.
3 errors corrected: Fixed £12k rounding difference in Fixed Assets Note. Corrected "Administrative expenses" tag (was "Other operating expenses"). Added missing "Small company exemptions" disclosure tag.
READY FOR LIVE SUBMISSION — All validation checks passed. File can be submitted to HMRC without risk of rejection. Estimated processing time: 1-3 working days after submission.
If HMRC rejects your filing due to tagging error (not client data error), we fix and resubmit at no extra charge. Plus cover any late filing penalties up to £500.
Historical rejection rate: 13 rejections out of 4,247 filings (0.31%). 7 were client data errors (we flagged but client approved anyway). 4 were deprecated taxonomy elements (FRC released schema update mid-filing). 2 were Companies House number mismatches (client gave us wrong number). Zero attributable to validation failure.
Layers 1 & 2 (schema + business rules): 10-15 minutes automated. Layer 3 (HMRC Gateway test): 5-10 minutes (depends on HMRC server response time). Total: 15-25 minutes. FCA NSM validation (listed companies only): additional 2-4 hours for ESEF format compliance and NSM staging test submission. Included in our same-day turnaround for standard filings.
We flag but don't fix underlying accounting errors (we're not auditors). Example: balance sheet doesn't balance by £50k. Validation report lists the issue, we put filing on hold, contact you with explanation. You provide corrected accounts, we re-tag and re-validate at no extra charge. If error is minor (e.g., £1 rounding), we fix it automatically and note it in validation report for your approval.
Free consultation includes basic validation check (upload your accounts, we run Layer 1 & 2 checks, report back on any issues found). Full validation report (including HMRC Gateway test submission) provided after payment as part of complete service. We don't test-submit to live HMRC Gateway until you've approved final file and authorized submission—test submission is final pre-flight check before live filing.
Gateway test submission uses HMRC's dedicated test endpoint. Same validation as live submission, but doesn't actually file the accounts. Test submission is not permanent—doesn't create official HMRC record, doesn't satisfy Corporation Tax filing deadline. After test passes, we then make live submission to production HMRC Gateway (this one counts). Test endpoint occasionally unavailable (HMRC maintenance windows)—in those cases we skip Layer 3 and rely on Layers 1 & 2, then monitor live submission closely for instant error response.
See how validation report looks in client portal. Preview side-by-side comparison.
Client Portal Free Validation Check
