UK Tax Deadlines Every Startup Should Know

Chosen theme: UK Tax Deadlines Every Startup Should Know. Launch with clarity, avoid penalties, and grow with confidence by mastering the dates that shape your first year and beyond. Subscribe for timely reminders and founder-friendly checklists.

Registering for Corporation Tax within 3 Months

As soon as you start trading, you must register for Corporation Tax with HMRC within three months. Many founders wrongly wait for their first sale; in reality, marketing spend or signing suppliers can be enough to count as trading. Set a reminder now, and comment if you want our registration checklist.

Setting Your Accounting Period and Aligning Deadlines

Your first accounting period drives nearly every other deadline. Decide on a year-end that fits your cash cycle, investor reporting, and product roadmap. Align payroll, VAT, and reporting rhythms to this date. If you’ve already picked one, tell us why—your story may help another founder choose wisely.

A Founder’s Early Reminder

Amelia launched a SaaS pilot in May, then forgot to register for Corporation Tax. A teammate flagged it in July, and they registered the same day—no penalty, just relief. The lesson: don’t wait for revenue to count as trading. Bookmark this section and subscribe for automated deadline nudges.

Corporation Tax: Payment, Return, and Penalties

If your company is not large enough for quarterly instalments, Corporation Tax must be paid nine months and one day after the end of your accounting period. That payment date arrives before the return is due, which surprises many. Add it to your calendar and share your accounting period end below.

VAT: Thresholds, Registration, and Return Due Dates

If your rolling 12-month taxable turnover exceeds £90,000, you must register for VAT—usually within 30 days of exceeding the threshold. Many startups register voluntarily earlier to reclaim input VAT. Tell us your model; we’ll share whether early registration commonly helps similar founders.

Payroll and PAYE: Real-Time Information Done Right

Before your first payday, register as an employer with HMRC. File a Full Payment Submission (FPS) on or before each payday under Real-Time Information rules. Late or missing FPS can trigger penalties. Create a payroll calendar and rehearse a mock run once. Need a template? Subscribe and we’ll share one.

Payroll and PAYE: Real-Time Information Done Right

PAYE and National Insurance are usually due by the 22nd of the following month if paying electronically, or the 19th if by post. Small employers may be eligible to pay quarterly. Automate payment through your bank with accurate references to avoid misallocation. Comment “PAYE” for our reference guide.

Self Assessment for Founders: Key Personal Deadlines

If you need to submit a Self Assessment, register with HMRC by 5 October following the end of the tax year. New directors, dividend recipients, and side-hustlers often fall into scope. Unsure whether you must file? Ask in the comments, and we’ll point you to the relevant HMRC guidance.

Self Assessment for Founders: Key Personal Deadlines

Online filing for the prior tax year and the balancing payment are due by 31 January. That same date often includes your first payment on account. Waiting until the last week risks identity checks and portal slowdowns. Subscribe for our calm, four-week countdown checklist to avoid a scramble.

R&D and Reliefs: Don’t Miss the Window

You typically have two years from the end of your accounting period to amend your Corporation Tax return and include an R&D claim. Keep contemporaneous technical notes and cost records to evidence eligibility. Thinking about claiming? Subscribe for our evidence workbook and planning prompts.