When will P21 underpayment be taken

[grotty]

Hi all - I asked this as part of another thread and it didnt get picked up - hoping you can help: I requested 3 years to be p21 balanced- one was correct, one year I was owed money and in the last I owed money. Re the last incident, there were no instructions in the letter received about when I have to pay the underpayment back - does anyone know if it will just be taken from my tax on my next payday...this would not be good!
Thanks

 

[STEINER]

It won't be taken from your next payday. Any changes in your pay arise when Revenue send you and your employer an amended tax credit cert.

How much is involved, a few hundred or a few thousand?

If its not a huge sum involved they probably will offset your refund vs your liability and either amend your 2012 tax credit which will impact on your net pay this year; or incorporate what you owe in your 2013 tax credits.