Moved: Do I need a NIN?

I originally posted this on the "on the job" board but it was suggested I post it here as well.

I am relocating to the UK in July and there is a strong possibility that I will continue working for my current US-based company remotely for the rest of the year.  Since my company is only in the US and I will be paid in $ and not earning any income from a UK-based company, will I still need to apply for a NIN and make contributions?  From what I have read elsewhere, there is a social security agreement between the 2 countries and all my employer would have to do is apply for a certificate from US Social Security that basically states I am contributing to this country's system and would be exempt from making contributions to the UK system.   

Working in the UK for a US employer for five years or less

The US authorities will give you and your employer a certificate showing
that you continue to pay contributions to the US scheme while you work in the UK.
If an officer from HM Revenue and Customs asks why UK contributions are
not being paid for you, show the certificate.

But, after looking at the application form (https://s044a90.ssa.gov/apps6z/coc_db/country_form.jsp?ctr_code=UK&ctr=United%20Kingdom&czn=U.K.&tp=2), it looks like it only applies for companies that have a presence in the UK (it asks for employer UK address).  Are there any information resources on telecommuting from the UK?  My company may or may not wish to go the route of applying for a certificate so in that case would I just have to make contributions to National Insurance myself?  I just want to make sure I'm covering all my bases here.

Thanks.

You can remain in the US SS system and not pay into the NI system.  However, your employer may have to pay into PAYE.  Your employer's HR department should hire a UK payroll tax specialist to make arrangements for either PAYE or modified PAYE, depending on you and your employer's specific needs.  It should not be you doing this, it should be them.

I can provide references to payroll tax companies offline.

IRS Circular 230 Disclosure:  To ensure compliance with requirements imposed by the U.S. Internal Revenue Service, we inform you that any tax advice contained in this communication (including any attachments) was not intended or written to be used, and cannot be used, by any taxpayer for the purpose of (1) avoiding tax-related penalties under the U.S. Internal Revenue Code or (2) promoting, marketing or recommending to another party any tax-related matters addressed herein.

1. As Lizzit says, moving to the UK from the US puts you in the position of the US/UK social security totalisation agreement.  This entitles you to remain in FICA for up to 5 years, so no need to pay NI or to get a a number.

2.  However once you are working here your earnings become subject to UK tax, so you'll want personal advice on reducing this and getting the 401(k) plan approved in the UK.
Neither PAYE or modified PAYE apply as there is no UK employer.  Lizzit is not a UK qualified practitioner so will not be familiar enough with the UK withholding side of things.  You do not need a UK payroll company of any kind.  You do need a qualified UK tax adviser.

3. The company will also want/need to get involved to ensure that your presence in the UK does not constitute a permanent establishment, so subjecting it to UK corporate tax.  In addition the company will need to review its transfer pricing and VAT obligations.  Therefore the company will need to do some research and take its own UK accounting advice.

4. Once you are in the UK you will be subject to UK employment law (contracts, maternity leave/paternity leave, vacation entitlement, minimum wage etc etc).  All of this compliance adds to the company's burden, so the company will need both a UK lawyer and accountant to organise itself.  This cannot be done inexpensively without failures that may cost you or the employer some money.

Guya,

Agreed on all points regarding work to be done by her employer but one:  Taxpayers no longer require corresponding approval for a 401k plan.  The new treaty specifically lists any US qualified plan (of which 401ks would necessarily count) as allowable reciprocal plans in the Technical Explanation for Article 18.

IRS Circular 230 Disclosure:  To ensure compliance with requirements imposed by the U.S. Internal Revenue Service, we inform you that any tax advice contained in this communication (including any attachments) was not intended or written to be used, and cannot be used, by any taxpayer for the purpose of (1) avoiding tax-related penalties under the U.S. Internal Revenue Code or (2) promoting, marketing or recommending to another party any tax-related matters addressed herein.