Carol Pusey, who taught at Whitefield secondary school in Cricklewood, north-west London, was found guilty of unacceptable professional conduct by England's General Teaching Council in Birmingham.
The committee heard that Miss Pusey worked for nine days as a supply teacher at eight different schools in Hertfordshire while she was still being paid by Whitefield school.
These included five days in September and October 2003 while she was on authorised leave and four days in November 2003 and April 2004 when she was supposedly off sick.
Miss Pusey, from Luton, who was not present at the hearing, began working at Whitefield as an IT teacher in January 2001.
Peter Blenkinsop, the headteacher, told the panel there had been problems with her conduct towards other members of staff. She began teaching English as a second language after falling out with her head of department.
"She was not particularly liked. There were concerns over her teaching and her relationship with staff," said Mr Blenkinsop said. "She also took a lot of time off which caused problems." After continued poor performance, Miss Pusey verbally agreed to resign in May 2003 and was given three months'
But she did not write a resignation letter and insisted on returning to the school on October 6 after taking sick leave, supposedly because of asthma.
Mr Blenkinsop heard about Miss Pusey's supply work from an ex-teacher in June 2004. She resigned the following month.