Emergency Tax in First Month?

I've just started a new job, and am supposed to have my P45 in by tomorrow. I don't want to do this I was to submit a tax clearance cert instead, but this will take a few days. As the cut off date for HR is tomorrow, will I get Emergency tax on my first pay cheque? I was told by a friend that the first pay cheque gets taxed normally, only after that does the high emergency tax rate kick in.

The way my job works I get a large 'training bonus' in the first month, but don't want to get taced on it at 42%/50%.
Thanks

I'm not sure what you mean about submitting a tax clearance cert instead of a P45 but if you call your local PAYE office, you will be able to advise them that you have changed employment & give them your new employer's name & PAYE number. Your new employer can then register you over the phone with revenue, who will more than likely give you month 1/temporary credits, which will be your normal tax credits for this payroll, you just won't get the benefit if you have not already used all your tax credits to date.