Hundreds of teachers who failed to secure new pound;2,000 "threshold" payments will be appealing against the decisions this half-term.
But they could have to wait up to seven weeks to hear whether they have won their cases or not.
Up to 90 per cent of experienced teachers are expected to have successful applications for the performance-related pound;2,000 rises. The Government is fully funding the award in England, so an extra pound;400million will go into teacher pay this school year. Many have already received the backdated payments.
One headteacher told The TES he had been seconded for 25 days, to work on 20 appeal cases. Around 50 people are being trained to do the reviews and can expect similar caseloads, meaning that as many as 1,000 appeals will take place this half-term, he said.
A Department for Education and Employment spokeswoman refused to comment on the number of appeals it expected, saying it was "early days" and that cases were still coming in.
"Each case will be reviewed by an individual review assessor who will be able to do all the hings the original threshold assessor was able to do - scrutinising evidence, and if necessary visiting the school. Reviews are expected to be completed in 70 working days," she added.
Cambridge Education Associates has been paid around pound;12m to run the threshold assessment and appeals processes - part of a pound;24m contract which also includes providing external advisers to help governors with appraisal of their headteachers.
Just under 1,200 schools have not requested an adviser visit, even though visits should have been completed in April. The original deadline was the end of last year, but administrative delays and problems getting advisers led to an extension of the deadline.
The DFEE said schools might not request an adviser visit because of a headteacher's extended sick leave, a vacant headship, or a governing body with an acting head wanting to wait until they made a permanent appointment. Some schools have had to postpone visits because of diary clashes, while others have closed or merged with other institutions.