File MTD ITSA vs 123 Sheets
123 Sheets is an established spreadsheet bridging tool with 35,000+ VAT users and strong security certifications. Their Income Tax product is in beta and not yet publicly available. File MTD ITSA is a purpose-built web platform for MTD Income Tax that's available now — covering all three income sources with a guided dashboard and full firm management portal. 123 Sheets is significantly cheaper; File MTD ITSA is significantly more complete.
Platform & Workflow
This is the fundamental difference between the two products. 123 Sheets is a spreadsheet bridging tool — you continue working in Excel (or Google Sheets, LibreOffice, etc.), insert their worksheet template into your existing spreadsheet, and upload it to the 123 Sheets website for HMRC submission. Your bookkeeping stays in your spreadsheet; 123 Sheets just handles the last mile of sending summary data to HMRC.
File MTD ITSA takes a different approach. It's a web-based platform where you enter your income and expenses directly into a guided quarterly dashboard, review your figures, and submit to HMRC with a single click. There's no spreadsheet to manage, no template to insert, and no file to upload — though you can import data via CSV if you prefer.
Which approach is better?
Neither is universally better — it depends on how you work. If your bookkeeping already lives in a spreadsheet and you want to keep it there, 123 Sheets' bridging approach avoids changing your workflow. If you want a dedicated dashboard that walks you through each quarterly submission step by step, File MTD ITSA removes the spreadsheet management overhead entirely.
Feature Comparison
| Feature | File MTD ITSA | 123 Sheets |
|---|---|---|
| Platform type | Web application (SaaS) | Spreadsheet bridging (upload) |
| ITSA publicly available | ✓ Live now | Beta only — contact to join |
| UK property income | ✓ | ✓ |
| Self-employment income | ✓ | ✓ |
| Foreign property income | ✓ | Not confirmed for ITSA |
| Quarterly submissions | ✓ One-click | ✓ Via upload |
| Year-end finalisation | ✓ | Beta — unclear |
| BSAS support | ✓ | Unknown |
| On-demand tax calculations | ✓ In-platform | Displayed from HMRC |
| Deadline reminders | ✓ Email alerts | ✗ Not mentioned |
| PDF reports | ✓ | ✗ |
| CSV import/export | ✓ | N/A (spreadsheet native) |
| Firm management portal | ✓ Full | ✗ Not for ITSA |
| Client impersonation | ✓ | ✗ |
| Firm branding | ✓ On PDFs/emails | ✗ |
| Sage/QuickBooks compatible | Via CSV import | ✓ Direct export upload |
| Works with Google Sheets | N/A (web-native) | ✓ |
| HMRC sandbox testing | ✓ | ✓ Demo available |
| Security certifications | SSL, bcrypt, UK servers | ISO27001, CE, CE+ |
Pricing
123 Sheets is substantially cheaper. Their ITSA licence costs around £19.75 per taxpayer per year (with a 50% first-year discount already applied in that price). That includes coverage for multiple self-employments plus UK and foreign property per taxpayer.
File MTD ITSA starts at £69 per year for the DIY plan. Assisted (with accountant review) is £199/year, and Done For You (full-service filing) is £399/year. Firm plans run from £299/year for up to 25 clients to £599/year for unlimited clients.
The pricing difference reflects the products' different scope. 123 Sheets provides the bridging layer between your spreadsheet and HMRC. File MTD ITSA provides the entire workflow — dashboard, guided data entry, tax calculations, annual adjustments, PDF reports, and firm management tools. If all you need is the submission bridge and you're happy managing everything in Excel, 123 Sheets delivers that at a fraction of the cost.
For Accountancy Firms
This is where the products diverge most sharply. File MTD ITSA has a dedicated firm portal with multi-client dashboards, client impersonation (file on behalf of a client without logging into their account), compliance status tracking across your entire client base, firm-branded PDFs and emails, team member accounts with role-based access, and bulk deadline notifications.
123 Sheets offers a Tax Agent login and multi-taxpayer licensing for their VAT product, but their ITSA product does not currently advertise equivalent firm management features. If you're an accountancy practice looking to manage MTD Income Tax filings for multiple clients from a single dashboard, File MTD ITSA is built for that workflow. If you're an accountant who files for clients one at a time using spreadsheets, 123 Sheets' approach may suit you at a lower cost.
Availability & Maturity
This is an important consideration. 123 Sheets' ITSA product is currently in beta. Their website invites users to contact them to join the beta, or sign up to be notified when the software is publicly available. Their main product — MTD for VAT — has a strong track record with over 35,000 entities and is used by top-15 accountancy firms.
File MTD ITSA is publicly available now with full access to all features during a 14-day free trial. The platform covers the complete MTD Income Tax lifecycle — quarterly submissions, BSAS, annual adjustments, and year-end finalisation — and has been tested against HMRC's sandbox and production APIs.
123 Sheets' VAT reputation is well earned, but their ITSA offering is still maturing. If you need production-ready Income Tax software for the April 2026 mandate, availability matters.
Security
Credit where it's due: 123 Sheets has stronger formal security certifications. They hold ISO 27001, Cyber Essentials, and Cyber Essentials Plus — all independently audited and government-recognised. Their servers are UK-based and payments are handled through WorldPay/Pay360.
File MTD ITSA uses 256-bit SSL encryption, bcrypt password hashing, encrypted HMRC token storage, and Stripe for payment processing (no card details stored). Servers are UK-based. While these are solid measures, we don't currently hold ISO 27001 or Cyber Essentials certifications. For organisations where formal certification is a procurement requirement, this is a genuine advantage for 123 Sheets.
Who Should Choose Which?
Choose File MTD ITSA if you:
- Want a web-based dashboard rather than managing spreadsheets
- Have foreign property income alongside UK property or self-employment
- Run an accountancy firm and need a multi-client management portal
- Want on-demand HMRC tax calculations and professional PDF reports
- Need production-ready ITSA software available right now
- Prefer a guided step-by-step quarterly workflow
Choose 123 Sheets if you:
- Already do your bookkeeping in Excel and want to stay there
- Use Sage or QuickBooks and want direct export-to-submission
- Need the lowest possible cost for basic ITSA bridging
- Already use 123 Sheets for VAT and want one provider for both
- Require ISO 27001 / Cyber Essentials certification from your provider
- Are happy to wait for the ITSA product to leave beta