R&D tax credits allow UK limited companies to reduce Corporation Tax or receive a cash repayment for developing new or improved products, software or processes where scientific or technological uncertainty existed. Claims must now follow strict HMRC compliance rules, including advance notification, a detailed technical narrative, an Additional Information Form and correct reporting on the CT600 tax return.

A complete, accountant-written guide covering corporation tax deadlines, payment rules, filing dates, penalties, interest charges, and how to avoid costly mistakes.

As a UK limited company, reducing your corporation tax bill legally and efficiently is one of the smartest ways to improve your cash flow and reinvest more money back into your business. But with HMRC scrutiny higher than ever, you need to ensure every tax-saving strategy is fully compliant, evidence-based, and professionally managed.

If the loan is repaid, released or written off, the company can claim repayment of the S.455 tax via HMRC’s L2P process or by amending the CT600A, depending on the timing.

This guide will help you get your 17-character corporation tax payment reference.

Everything you need to know about filing year end accounts to Companies House & HMRC.

In this guide, we explain what limited company tax is, how it’s calculated, what tax returns you need to submit, and tips to legally reduce your tax bill — all with updated information for the 2025/26 tax year.