i worked for three days (21 hrs) only for another company last month and got paid and a big chunk of it went to tax. i got taxed twice as much as if i'm working full 37.5hrs at my current job. i know you pay more tax for a second job, but surely cant be that much can it? it was only for three days... and the hourly rate is the same?
The tax figure could well be correct. You will pay tax at 20% (or 40% if you're into higher rate band) on the whole amount from the second job. On your first job you don't pay any tax on the first £6500 or so so the average tax rate on your first job is quite a lot less than 20%
I occasionally get second pay and it's always taxed at Basic Rate. If all your personal tax allowance is used up on your main job, then I'm afraid the second job will be taxed like this. You don't exactly pay more tax because you have a second job, you pay more because there are no allowances to be set against the second pay.
Much as it seems unfair, National Insurance is payable on every job you do.
However, unlike Income Tax (where your tax-free allowance normally gets used up totally by your first job) you're allowed to earn a certain amount before you pay National Insurance in every job. If you've not had NI deducted it means that you didn't reach the threshold to pay it. However, if your pay from your second job had been higher you'd still have had some NI to pay.
As Chris already said, you would have done had it been high enough earnings for the week. Being a one off is irrelevant. If you'd earned £150 as a "one off" you'd have had NI to pay. Earning less than £110 you wouldn't.
Also to add that like buildersmate I can't see any benefit in dotty's suggestion of getting your tax code split between the two jobs (though you can if you really want to for some reason).
The only point in that would be if you didn't actually use all of it in job 1. If you do then there's no benefit to be had by switching the allowances about.