Prepare for Software-Only Filing: Complete Guide
Two major deadlines are approaching that require you to switch from free government services to commercial software. Here's how to prepare.
The Two Deadlines
| Service | Closes | What Changes |
|---|---|---|
| HMRC CT600 | 31 March 2026 | Must use software for Corporation Tax |
| Companies House WebFiling | 1 April 2027 | Must use software for accounts |
Your Preparation Timeline
Now (12+ months before)
- Download HMRC CT600 filing history
- Research software options
- Understand your company's needs
6 Months Before CT600 Deadline (Sept 2025)
- Choose CT600 software
- Create account
- Set up HMRC connection
3 Months Before CT600 Deadline (Dec 2025)
- File at least one return through new software
- Verify successful submission
- Resolve any issues
March 2026: HMRC Deadline
- Fully transitioned for CT600
- No longer using HMRC's free service
6 Months Before CH Deadline (Sept 2026)
- Ensure software also handles Companies House
- Or choose separate accounts software
- Test accounts preparation
April 2027: Companies House Deadline
- Fully transitioned for accounts
- Using software for all filings
Choosing the Right Software
For Combined CT600 + Accounts
Best efficiency — one software for everything:- TinyTax (free for micro-entities)
- TaxCalc (paid)
- IRIS (paid)
For CT600 Only
If you want separate solutions:- Any HMRC-recognised software
- Consider future accounts needs
For Accounts Only
Less common but possible:- Some software handles CH only
- Usually better to combine
What to Look For
Essential Features
- HMRC-recognised for CT600
- Companies House filing capability
- iXBRL generation (automatic)
- Error validation
Nice to Have
- Trial balance import
- Tax calculation
- Prior year comparatives
- Multiple company support
Free vs Paid
| Feature | Free (TinyTax) | Paid Options |
|---|---|---|
| CT600 filing | ✓ | ✓ |
| iXBRL accounts | ✓ | ✓ |
| Companies House | ✓ | ✓ |
| Multi-company | Limited | ✓ |
| Practice tools | ✗ | ✓ |
| Price | £0 | £100–£300+/yr |
Common Preparation Mistakes
Waiting Too Long
Don't wait until March 2026 or April 2027. Start now to:- Learn software without pressure
- Resolve issues before deadlines
- File with confidence
Not Downloading History
You'll lose access to HMRC's records after closure. Download now.Choosing Complex Software
If you're a small company, you don't need accountant-level software. TinyTax is purpose-built for small company filing.Forgetting Companies House
Many focus on CT600 deadline (2026) but forget accounts deadline (2027). Prepare for both.Summary
- Two deadlines: HMRC March 2026, CH April 2027
- Start preparing now
- Download HMRC history immediately
- Choose software that handles both
- Test before deadlines
TinyTax handles both CT600 and accounts filing. Get started free →