Guide · February 2026
CT600 vs SA100: Which Tax Return Do You Need?
One of the most common confusions for UK company directors: you might need to file both a company tax return and a personal one. Here is when each applies and why.
The basics
| CT600 | SA100 | |
|---|---|---|
| Who files it | Limited companies | Individuals |
| Tax covered | Corporation Tax | Income Tax, Capital Gains Tax, NI |
| Period | Company's accounting period (usually 12 months) | 6 April – 5 April (tax year) |
| Filing deadline | 12 months after period end | 31 January (online) after the tax year |
| Payment deadline | 9 months + 1 day after period end | 31 January (with payments on account in July) |
| Rates (2025/26) | 19% / 25% | 20% / 40% / 45% |
When you need both
If you are a director of a limited company, you almost certainly need both. Here is why:
- •Your company files a CT600 to report its profits and pay Corporation Tax on them
- •You personally file an SA100 to report your salary, dividends from the company, and any other personal income
The company and you are separate legal entities. The company pays its tax; you pay yours. Dividends are taxed twice — once as corporate profits (Corporation Tax) and again as personal income (dividend tax rates).
When you only need an SA100
- •You are a sole trader (not a limited company)
- •You are in a partnership (LLP or general partnership)
- •You have rental income, investment income, or other untaxed income but no company
When you only need a CT600
Rare for directors, but possible if you do not take a salary or dividends from the company (for example, a holding company with no personal drawings). In practice, most directors take at least a small salary for the NI credit, which triggers SA100 obligations.
Common mistakes
Filing SA100 instead of CT600. Self Assessment is for people, not companies. If you have a Ltd company, its profits go on a CT600. Your drawings from the company go on your SA100.
Forgetting to report dividends. Dividends you take from your company must go on your SA100, even though the company already paid Corporation Tax on those profits. The dividend tax rates (8.75% basic, 33.75% higher) apply above the £500 dividend allowance.
Missing the different deadlines. CT600 and SA100 have completely different filing and payment dates. Set reminders for both.
File both with Taxentis
Taxentis handles CT600 filing for your company and SA100 for your personal tax — all in one place. Look up your company, enter your figures, and submit directly to HMRC.