Self employed whilst also in full-time employment?

[danuk]

I am currently in full time employment, however, I'm looking into the possibility of doing some self employed work on the side.

I am a little confused about the tax / ni issues in this situation.  Everything I have read so far applies to the self employed work being the sole source of income.

Will tax be applied to my entire income as a whole or will each source be taxed separately?
Will my current employer need to alter anything in my pay or do I just need to work out what I owe based on whatever else I make in the self employed job?

Finally, I have also read that class 4 ni contributions are only applicable once you are earning over a certain amount.  Again, is this based on my total income or just that of the self employed stuff?

I'm only expecting to make a small amount from this initially (less than 5000 per year). My salary from my main job is 18000.

Can anyone help me clarify any of these points?

Any advice appreciated.

Thanks.

[pawncob]

Tax will be applied to each part of your income. PAYE will continue, Schedule D will apply to S/E income.
Tax on S/E due twice a year in Jan and July.
Employer will not know about S/E (unless you tell him)
Class 4 applies to S/E income over £7225 p.a. @9%.

[King_Maker]

Have you read HMRC's "Starting in Business"?

http://www.hmrc.gov.uk/startingup/

[danuk]

I am in the process of working my way through it. I was just weary of anything that might catch me out, having two separate sets of income.

Thanks again.

[King_Maker]

You may need to pay Class 2 NIC also - currently a flat rate of £2.50 per week.

The Small Earnings Exception for 2011-12 is £5315. In strictness, Certificate backdating of up to 13 weeks only is permitted - but can be extended.