How do you deal with the out of phase UK and US tax years?

The US has a tax year that runs from Jan 1st to Dec 31st; the UK's runs from April 6th to April 5th of the next year.

This is produces "chicken and egg" tax situations. So what do you do.

99% of my taxable income will arise in the US, so when I have to do UK taxes I was thinking about just using my annual US numbers to fill out the next years UK forms. In essence I'd be using my Jan to Apr US tax numbers from one year as an estimate for my UK taxes. I believe HMRC allows you to make an estimate if you don't have the figures yet. In this scenario lets say I'm filing UK taxes for Apr 6th 2011 to Apr 5th 2012. I have my US tax figures for Jan 1st 2011 to Dec 1st 2011 already, but I won't have the US numbers for Jan 1st 2012 to Apr 5th 2012 until early 2013 so I just use my US tax figures for Jan 1st to Apr 5th 2011. If I continue to do this the aggregate tax should work out just fine and I won't be pressurized by deadlines.

The other way would be to wait until I had all the information from two US tax filings so that I could construct a full UK tax year. As the online deadline for the UK Apr 6th 2011 to Apr 5th 2012 tax filing is Jan 31st 2013 I could wait to file and hope that all my US tax forms arrived in early Jan and get my US taxes done. Then pro rate and combine the figures from the US Apr 5th to Dec 31st 2011 and Jan 1st to Apr 6th 2012 onto my UK return. This sounds complex and I'd probably have an aneurysm some time in  january 2013.

I worried about this also but since my US sourced income is pretty regular in practice it's been quite easy.
I'm a USC resident in the UK and I get social security from the US. The UK taxes this as per the treaty. There is no witholding tax on this so every year I owe the UK tax for the whole year of Social security income.

I didn't pay any UK estimated tax on this income for the first year - I just did the UK return and paid the tax bill at the end. So, I declared 12 months of US social security (april 2009-march 2010) Then, in the following years, the amount of estimated tax I pay is based on my previous year's income as I reported it on the UK tax form. ie, for 2010-11, the estimate is calculated  on what declared for 2009-10. Also, once you pay a year of estimated tax, your local tax office will send you a 'tax bill' showing your estimated tax calculated in this way. (If your income will change for your current tax year, up or down, you write them back and they will send you a new bill, showing the correct amount you will owe.) As long as your US income doesn't vary widely, it has its own little rhythm and isn't really a problem.

When I first started thinking of these issues this is the one I found the most perplexing. I asked HMRC (international specialist) about it. The person I spoke to was equally vague and what I carried away was 'just prorate it'.

I just use the bit at top of the  tax form where it gives you the option to enter your own dates.. I just use the UK tax year dates. Simmmples

Edited to add all my income is UK.. so your mileage may vary 

I just use the bit at top of the  tax form where it gives you the option to enter your own dates.. I just use the UK tax year dates. Simmmples

Edited to add all my income is UK.. so your mileage may vary 

I can agree that an individual can elect a non-calendar year accounting year for US tax purposes, but this is both permanent (it is not an election that can ever be revoked) and extremely unusual. In fact I have only see this once in the last 30 years in professional tax practice.  One would need to learn the relevant parts of the IRS code and regulations that permit such an election to ensure that income, credits, deductions, exclusions etc are properly claimed each year. 

I just use the bit at top of the  tax form where it gives you the option to enter your own dates.. I just use the UK tax year dates. Simmmples

Edited to add all my income is UK.. so your mileage may vary 

If you have US income this would surely make this even more complicated as your tax forms like 1099s etc report from Jan 1st to Dec 31st

I can agree that an individual can elect a non-calendar year accounting year for US tax purposes, but this is both permanent (it is not an election that can ever be revoked) and extremely unusual. In fact I have only see this once in the last 30 years in professional tax practice.  One would need to learn the relevant parts of the IRS code and regulations that permit such an election to ensure that income, credits, deductions, exclusions etc are properly claimed each year. 

To change to a non-calendar year it seems you need to get IRS approval: http://www.irs.gov/businesses/small/article/0,,id=98673,00.html