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HMRC letter codes · National Insurance (CA)

CA3837Certificate for working temporarily abroad while self-employed

Last reviewed 14 October 2026 · How Tax Letters checks its facts

In short

GOV.UK lists the CA3837 as the form to apply for a certificate confirming you will pay UK National Insurance while self-employed abroad temporarily, and its page describes it as for a self-employed individual working temporarily in an EU country, Gibraltar, Iceland, Liechtenstein, Norway or Switzerland.

“Apply for a certificate to confirm you will pay UK National Insurance while self-employed abroad temporarily (CA3837) … a self-employed individual working temporarily in an EU country, Gibraltar, Iceland, Liechtenstein, Norway or Switzerland”

GOV.UK: Apply for a certificate to confirm you will pay UK National Insurance while self-employed abroad temporarily (CA3837) · checked 14 October 2026

Information, not advice: this page reports what HMRC, GOV.UK and the bodies named publish about CA3837. Each fact has its source and the day it was checked beside it.

What it is

GOV.UK says the CA3837 form can be used by a self-employed individual or their agent.

“You can use this form if you’re a self-employed individual or their agent.”

GOV.UK: Apply for a certificate to confirm you will pay UK National Insurance while self-employed abroad temporarily (CA3837) · checked 14 October 2026

What it asks

GOV.UK's CA3837 page lists what you need to apply, including the address of your self-employed business and the type of work you carry out both in the UK and abroad.

“the address of your self-employed business … the type of work you carry out both in the UK and abroad”

GOV.UK: Apply for a certificate to confirm you will pay UK National Insurance while self-employed abroad temporarily (CA3837) · checked 14 October 2026

GOV.UK's CA3837 page says an agent's client needs to fill in an authorising your agent (64-8) form, and the completed form is submitted with the CA3837 application form.

“your client needs to fill in an authorising your agent (64-8) form. You should submit the completed form with your CA3837 application form.”

GOV.UK: Apply for a certificate to confirm you will pay UK National Insurance while self-employed abroad temporarily (CA3837) · checked 14 October 2026

Time limits and rules

GOV.UK's CA3837 page says you cannot apply more than 12 months in advance.

“You cannot apply more than 12 months in advance.”

GOV.UK: Apply for a certificate to confirm you will pay UK National Insurance while self-employed abroad temporarily (CA3837) · checked 14 October 2026

How to send it or apply

GOV.UK's CA3837 page says you apply online by signing in (creating sign in details if you do not have them), and that you can save your answers and return later.

“You’ll need to sign in to use this service. If you do not already have sign in details, you’ll be able to create them. … You do not have to fill in the form in one go. You can save your answers and return later.”

GOV.UK: Apply for a certificate to confirm you will pay UK National Insurance while self-employed abroad temporarily (CA3837) · checked 14 October 2026

Free help and HMRC contacts

If you have a question about a certificate of coverage, such as one about CA3837, GOV.UK’s National Insurance enquiries page says to call HMRC on 0300 200 3500. Lines are open Monday to Friday, 8am to 6pm, and the page links to “Find out about call charges”.

“Call HMRC for help and information with: … certificate of coverage (also known as a PDA1 or A1) queries … Telephone: 0300 200 3500 … Opening times: Monday to Friday, 8am to 6pm. … Find out about call charges”

GOV.UK: National Insurance: enquiries · checked 14 October 2026

Free help first

These routes are described by GOV.UK, TaxAid and Citizens Advice themselves.

  • HMRC's extra supportHMRC offers extra support if your health condition or personal circumstances make it difficult to contact HMRC, for example a mental health condition, financial hardship or being treated in hospital.
  • Someone to deal with HMRC for youYou can authorise a friend, relative or voluntary organisation to talk to HMRC for you and help you fill in forms.
  • TaxAidTaxAid helps people with tax problems who cannot pay for advice. Tax Help for Older People merged with TaxAid in July 2025.
  • Citizens AdviceCitizens Advice gives confidential advice online, over the phone and in person, for free.