UK Financial Update - September 2026: Tax Deadlines, HMRC Rates & What to Prepare For

September is a useful time for both companies and individuals on the UK tax year to review the financial situation, and in doing so to assess deadlines and prepare for developments that can affect business and personal cash flow. With changing HMRC and Bank of England interest rates, changes to National Insurance contributions and to aspects of Making Tax Digital legislation, staying informed can assist with avoiding costly outlay for a business.

The accounting, tax and financial obligations of companies and individuals are supported by FMLLP. Please see a September 2026 summary for guidance regarding some of the key information business and individuals may require:

HMRC Late Payment Interest Rate September 2026

Payments made by both companies and individuals to HMRC will incur additional interest if they arrive after the set due date. Since 9 January 2026 the standard HMRC late payment interest rate has been 7.75%. As well as this figure, there is an associated rate for late payment of Corporation Tax, among several others. The HMRC interest rate is currently fixed in relation to a change in Bank of England base rate.

Businesses need to plan for the cost of tax. Planning adequate provisions for PAYE, Corporation Tax and VAT, as well as several other taxes, can ensure there is no potential to incur fines or interest.

Corporation Tax Deadline 2026

For the majority of companies, Corporation Tax falls due within 9 months and 1 day of the end of its financial year, where the Corporation Tax Return may become due within 12 months from the year-end, depending on the company's accounting date. For example, a company with a December year-end will ordinarily have until 1st October to pay Corporation Tax, before 1st November in respect of the Company Tax Return in most instances. Companies cannot afford to wait until their deadline arrives to ensure cash flow requirements can be met, and the value of preparing accounts in advance can help establish clarity.

VAT Registration Threshold 2026

Businesses must observe the registration threshold of £90,000 for taxable turnover. This rule means any taxable turnover above the threshold should trigger registration, unless an application is made to be voluntarily registered if some level of turnover is below £90,000. For the purposes of deregistration, the threshold is £88,000. Businesses should endeavour not to exceed £90,000 taxable turnover in any taxable year if not in a registerable business; this can be more difficult to detect accurately than simply identifying an obvious threshold crossing.

Making Tax Digital ITSA 2026 - Who is affected?

From April 2026, businesses, landlords and sole traders within this group will need to make regular submissions through tax software, under what the legislation calls Making Tax Digital for Income Tax (MTD ITSA). This initially applies to most solely employed entities and landlords where relevant income exceeds £50,000; more businesses fall under its mandate as the system progresses, so checking requirements closely is advisable. Individuals, sole traders and landlords who may qualify should check their systems to ensure their existing setup is compliant, or that necessary changes are made if not.

Bank of England Base Rate September 2026

The Bank Rate that was set for September 2026 stands at 3.75%, where another Bank Rate decision is expected on the 17th September 2026. Borrowing and mortgage costs and interest, for both individuals and businesses with loans and businesses who use credit facilities, can be indirectly or directly impacted by fluctuations to the Bank Rate. Businesses with significant credit outlays might want to consider implications from changing lending or lending practices.

Class 1 National Insurance Rate 2026

With changes in April 2026, the standard Class 1 employer's National Insurance rate sits at 15% of most earnings over secondary threshold limits, with employees having contributions at 8%, with a 2% above an upper earnings limit. National Insurance should always be considered when looking to manage payroll expenses for staff, especially during salary review stages and the onboarding or development process of a recruitment drive.

Prepare as Follows

• Calculate current payments and those due
• Check business and personal cash reserves, including Corporation Tax provisions
• Track sales against the VAT threshold
• Identify if any business operations have become applicable to MTD ITSA
• Account for changing payroll and National Insurance payments
• Plan around possible variations in Bank of England base rates
• Contact an advisor about potential year-end planning or for any queries

Keeping up to date with financial records and an overview of liabilities allows for effective long-term business decisions. For accounting, tax and business support, consult with FMLLP.

FAQs

Q1. What's the prevailing September 2026 late tax payment interest rate charged by HMRC?

As of September 2026, individuals and companies incur a 7.75% interest rate on tax payments that are made past the deadline; rates will vary along with the Bank of England base rate.

Q2. What is the required VAT registration threshold figure?

The VAT registration threshold from April 2026 stands at £90,000 for most relevant taxable turnover in an accounting year. Those wishing to deregister need to have had taxable turnover under £88,000 over the preceding year to a deregistration period.

Q3. Which people or entities is MTD ITSA legislation set to impact from 2026 onwards?

All landlords and sole traders with respective taxable earnings above £50,000 from April 2026 are to begin utilising compatible software. Details should be checked on the government website, however, as individual liabilities will vary greatly depending on the type of enterprise, etc.