Self Assessment deadline: scam alert, interest costs, and HMRC digital letters

Late January is the peak period for Self Assessment stress, and it is also peak season for phishing and missed messages.

A few simple checks can reduce risk and help you stay in control.

Scam activity rises ahead of 31 January

HMRC has warned that more than 4,800 Self Assessment scams have been reported since February 2025. It has also received over 135,500 reports of suspected HMRC related scams in the last 10 months, including scams that pretend to be tax refunds.

Scammers rely on timing and pressure. They know people expect HMRC contact in January, so fake demands and fake refund offers are more likely to catch someone off guard.

What to look out for:

• Urgency and threats: “final notice”, “immediate action”, “criminal prosecution”
• Links that ask you to sign in, confirm details, or “unlock” a refund
• Unfamiliar email addresses, shortened links, or unusual wording
• Requests for personal information or bank details

What to do if you are unsure:

• Do not click links or download attachments
• Do not call numbers included in the suspicious message
• Use official GOV.UK routes to check whether contact is genuine and to report suspected scams

Late payment interest adds cost quickly

Missing the payment deadline does not just trigger penalties; it also triggers interest that accrues until the tax is paid.

HMRC’s published rates show:

• Late payment interest: 7.75% from 9 January 2026
• Repayment interest: 2.75% from 9 January 2026

Even if you plan to file on time, it is worth checking your cashflow plan now. If you need time to pay, you will get better outcomes by addressing it early rather than after the deadline.

HMRC letters are moving into your HMRC account

From Spring 2026, HMRC expects to operate a “digital by default” model for many outbound communications for customers using digital services, with a gradual rollout as systems become ready. Opt-out is expected for those who need postal communications, and digitally excluded customers should continue to receive paper letters.

This change increases the chance of “I did not see the letter” problems, especially if a taxpayer rarely logs in.

Practical steps:

• Log in to your HMRC account and check for new messages
• Make sure your contact details are correct
• Enable notifications where available
• Keep a simple monthly reminder to check the account, especially around filing deadlines

Quick checklist for this week

• Confirm you have everything needed to file
• Treat unexpected HMRC messages as suspicious until verified
• Plan the payment and make it before 31 January where possible
• Check your HMRC account access and notifications

How can Oldfield help you?

If you would like us to complete your return, confirm what needs reporting, or help you with your wider accounting or tax needs, please get in touch.

Please note: This article is for general information purposes only and was correct as at the time of writing (14/01/26) and does not constitute financial advice. Tax rules and legislation are subject to change, and their application depends on your individual circumstances. We recommend seeking advice from a suitably qualified tax adviser, and where relevant, an FCA-authorised financial planner. Any lists and details provided above are not exhaustive and are not intended to be full and complete guidance. No action should be taken without consulting detailed legislation or seeking independent professional advice. Therefore, no responsibility for loss occasioned by any person acting or refraining from action as a result of the material contained in this article can be accepted.