Self employed to employed

I’m thinking of leaving self employment and getting a job. Has anyone ever done this and how did you go about it regarding tax? Obviously I currently submit a tax return every year, but what I’m worried about is that if I take a job I will end up paying more tax than would be normal until everything is sorted out. Taking on a job will probably result in less money, but I can’t afford to take a big reduction even if I get it back eventually.