HMRC is coming for your savings - Watch out for scams asking for your NI number

17th August 2025

HMRC and the government are moving to make NI numbers routine for savers — ISA managers already must take them for new accounts, and banks/building societies will be required to collect NI numbers for (ordinary) savings accounts under rules being introduced for April 2027.

What that means for you

ISAs: From 6 April 2025 new ISA applications must include the investor's National Insurance number (unless they're not eligible to have one).
GOV.UK

Other savings accounts
New rules reported and being legislated will require savings providers to make "reasonable efforts" to obtain NI numbers for new and existing interest-bearing savings accounts from April 2027. This is to help HMRC match interest data and collect tax automatically (via PAYE/tax-code adjustments) where needed.

If you've been asked to provide your NI number
First check the request is genuine (HMRC guidance on spotting scam letters/emails). If it's from your bank it's normal for them to request it if they’re updating records.

You can find your NI number on payslips, P60s, your Personal Tax Account, or via the HMRC app; GOV.UK explains how to retrieve it or ask HMRC for confirmation.

Who this might be awkward for
People without an NI number (young children, some non-working foreign nationals, older people who never had one) may need to apply or follow special handling — providers are expected to allow for those cases.

Consequences of refusing to give your NI number to the bank
It depends on the type of account — but you can’t always just refuse without consequences. What happens varies:

Key outcomes

ISAs (Individual Savings Accounts)
from 6 April 2027 an ISA manager must obtain an investor’s National Insurance number (or a declaration that the investor is not eligible for one) before a subscription can be accepted. If you refuse to give an NI number (and you’re eligible for one), the provider can refuse the subscription (i.e. they can stop you putting money into the ISA).

Ordinary savings accounts / other interest-bearing accounts
New rules being introduced for reporting to HMRC mean banks/building societies will be required to try to collect NI numbers for customers (policy rollout from 2027 has been widely reported). If you decline, the bank will usually record that no NI was supplied and still report interest and other data to HMRC — HMRC may then follow up, and may collect any tax due by adjusting your tax code or asking you to declare the interest. It’s unlikely to be a criminal offence simply to refuse, but refusing can make things more administratively awkward (and could lead the provider to restrict or refuse certain products).

Practical risks
If you give a false or incorrect NI (or say you don’t have one when you do), there can be compliance consequences — for example an ISA could be voided if the manager later finds incorrect provided information. So don’t invent numbers.

HMRC/banks will still have other identifiers (name, DOB, address). If you refuse the NI, HMRC can still try to match interest to you and may contact you about unpaid tax. News coverage says the government expects to use NI data to allow HMRC to collect tax via PAYE adjustments.

What you can do
Check why they’re asking — legitimate requests will come from your bank/building society (or HMRC). If it’s an email/phone call you weren’t expecting, verify it before giving sensitive information. HMRC has guidance on spotting scams.

If you don’t have an NI number tell them so and supply whatever proof they need; banks are expected to allow for people who are genuinely ineligible. GOV.UK explains how to get your NI number if you need one.

If the bank refuses a service or account, ask for a written reason and (if you think it’s unfair) contact Citizens Advice or the Financial Ombudsman for help. Citizens Advice can also help if you genuinely can’t open an account.

Bottom line
Refusing to hand over your NI number won’t automatically make you commit a crime, but for ISAs it will normally prevent you from subscribing (from 6 April 2027) and for savings accounts it will create reporting and tax-follow-up issues — and could limit what the bank is prepared to offer. If you’re unsure about the legitimacy of the request or about your eligibility for a National Insurance number, I can help you check the wording of the message you received (paste it in—make sure to remove any sensitive numbers) and suggest a safe next step.