The First 90 Days: Essential UK Compliance for New Business Startups
- elnasheikh
- Dec 2, 2025
- 2 min read
Just registered with Companies House? Here are the critical tax and legal deadlines you must meet in your first quarter as a UK Limited Company.
The excitement of launching a new UK business often overshadows the less glamorous, but critically important, task of compliance. The moment your company is incorporated, HMRC and Companies House expect you to meet strict deadlines. Failure to do so can result in immediate fines and penalties.
1. Registering for Corporation Tax
While you register your company with Companies House, you must also tell HMRC that the company is active and liable for Corporation Tax.
The UK Deadline:
3-Month Window: You must notify HMRC within three months of starting to do business (this includes buying, selling, trading, or hiring staff).
The Fine: Missing this registration deadline, even if you owe no tax, can result in a penalty. Once registered, HMRC will set a deadline for your first Corporation Tax return (CT600).
2. Setting Up PAYE If You Hire Staff (or Pay Yourself a Salary)
If your company pays anyone a salary, including yourself as a director, you must operate a Pay As You Earn (PAYE) scheme. This system deducts Income Tax and National Insurance Contributions (NICs) from salaries before they are paid.
The UK Requirement:
Real Time Information (RTI): PAYE operates on an RTI basis, meaning you must report payments to HMRC on or before the day the employee is paid.
Pensions Auto-Enrolment: Even if you only pay yourself, you must assess yourself for workplace pensions auto-enrolment. This is a crucial, often overlooked, legal requirement for UK companies.
3. Understanding Statutory Filing Requirements
Two key public bodies require documents from your UK Limited Company annually: Companies House and HMRC. The deadlines for these are based on the date of incorporation and the company’s year-end date.
The UK Filings:
Companies House: You must file a Confirmation Statement (annual check of company details) and a set of Statutory Accounts (usually abbreviated/dormant accounts for new companies). Missing the accounts deadline incurs escalating penalties.
HMRC: You must file the Corporation Tax Return (CT600), which requires your company’s financial records and tax calculations.
The Takeaway: Avoid Early Penalties
Starting a business is complex enough without the stress of unexpected HMRC fines. Establishing a proper financial and compliance framework in your first 90 days is the best investment you can make. By engaging with an accountant early, you ensure these crucial deadlines are met and that your business is structured for efficiency from day one.
Ready to start your UK Limited Company the right way? Let's build your compliance roadmap together. Schedule your initial startup consultation now.
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