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Sample SED computation

The following shows an example of how the SED computation works, but please contact Nicolson Accountancy for a discussion of your personal circumstances.

Mary is an Engineer on board a Merchant Navy vessel and has no other income.

  • She flies out at 11pm on 5 January 2009 to join her vessel in Ascension, before spending 4 months in the Antarctic.
  • Two months at home and then back to the Antarctic for another four months.
  • After a month at home, she heads off to see relatives for a month in Australia.
  • Thereafter, it is two months in the Gulf, servicing warships.
  • Due to a family wedding in the Summer of 2010, Mary has to miss her next trip and is ashore for almost 7 months.
  • Back off to the Gulf in October 2010, Mary cracks a couple of ribs on the ship and is flown back to hospital in the UK.
  • In January 2011, she is back to the Antarctic for six months.
Date outDate inDays outDays inTotal days1/2 totalCum days
in UK
Pass test?Comments
27/10/201025660Gulf – hospital

When Mary comes to prepare her 2008/09 Tax Return she doesn’t know if she has a qualifying period until a period of 365 days has elapsed.

The 2008/09 Tax Return is due in on 31/1/10, but her qualifying period doesn’t finish until 5/1/10. That doesn’t give much time to prepare and lodge her Tax Return.

On 5/10/10 Mary has a qualifying period, and as she has passed the test (Are the cumulative days in the UK less than half the total days?) on every occasion, then Mary can claim SED for all her income during the period 5/1/09 to 5/4/09 on her 2008/09 Tax Return.

All her income in 2009/10 qualifies for SED as she has a qualifying period of 365 days and passes every test.


As her accident means she does not have enough days to pass the test, only her income from 6/4/10 to 30/1/11 qualifies for SED on her 2010/11 Tax Return.


The entire SED calculation will start again on her next trip out of the UK, and Mary cannot have a new qualifying period until 30/1/12.

Where only part of the year qualifies, then the income from that source is normally apportioned simply by the number of days. However, there are other basis which can be more advantageous, and you should speak to us about this.

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