Wages and Tax

Hi All, I just started a new job recently. I received my first paycheck last week. I was payed significantly more in tax than I thought I would.



I think this is because I didn't hand my P45 in and maybe HMRC didnt get the correct number code in. My question is , will I get the money back once its resolved? And, will I buy overcharged again next month? How long do these things take? Thanks