NMM

My normal salary is below the £50270 40% tax bracket. BUT my company has had a very good year and the bonus this year will be quite high. This bonus will be paid in the March payslip. As a result I think my gross pay will be about £50200 so just under. However I will be getting about £650 bank interest this year. After reading HMRCs guidelines I 'think' this means I add the £650 to the gross pay which will take me over the 40% tax bracket.... I assume this means I will pay 20% still on my salary BUT that I will only get £500 tax free interest allowance. I have no issues paying the tax on the interest over the £500 BUT I would prefer HMRC not adjusting my tax code to do this. I used to have a small side business that I did a tax return for but this hasn't needed a retun for a few years as I haven't had time to pursue it. So, once I get my P60 for 23/24, can I submit a tax return to pay this tax or will HMRC (when my march payslip is done) automatically change my tax code from April? My bank says that interest is my responsibility to declare yet HMRC say the bank will inform HMRC. I obviously have every intention to pay this interest but at same time I don't want to pay it twice if HMRC won't give me the option to pay what I owe without adjusting the code. Do they send me a notification to tell me what I owe and the choice of paying in one go or via tax code. Apologies for the questions, this is the first time my income has ever done this