JW7121

I currently have a base salary of under £50,270 and have a tax code of 1275L, however i have been doing a lot of overtime this year and am approaching the £50,270 threshold. The overtime is voluntary so i can pick and choose. If i go over the £50,270 threshold will it change my tax code for next year? Also as we claim child benefit will i have to register for self assessment if i go over £50,270 or is that only if i go over £60,000?