Hello!

I have a quick question about taxes. I'm looking at a promotion next month, and I will be earning a few hundred more a month than I do currently - but that will put me into the higher tax band according to this income caculator. How does this affect my income? Will all of it be under the higher tax amount? I'm not totally sure what's going to happen with my income and if someone could explain it I would greatly appreciate it!

Thanks!