When starting a new job and the P45 hasn't yet appeared from the previous employer I seem to remember that most employers want to put you on emergency coding (which usually amounts to BR) until the P45 arrives.
Once upon a time you could ask to be put on "week 1 month 1" (or something similar) to make the deductions a bit more realistic.
Can anyone advise if this is still the case (and correct my probably incorrect terminology)?