Exam markers signed up to work for the Scottish Qualifications Authority this year without realising their pay could drop.
The SQA told its 7,000 markers last year that a new pay structure would be fairer and the "vast majority" would earn at least as much as in 2008-09, but failed to mention one crucial change.
The "general fee" has been removed, a fact that many will only have discovered months after agreeing to be markers. They were informed of the change last week by letter, in which the SQA apologised that "earlier communications did not make this clear".
The removal of the general fee means many markers expecting to be paid more this year will actually see their earnings fall. Even where they get an increase, it is likely to be much smaller than script fees suggest.
A spokesman said: "If there is a concern that confusion does exist about the removal of the general fee or any other part of the new system then, clearly, we should have been more explicit in our explanations to markers."
When asked whether the "vast majority" of markers would see no change in earnings even when the general fee's removal was factored in, he said: "We don't have that information to hand."
He added: "It is important to get across the message that, in real terms - that is, payment for the same task as undertaken previously - the majority of our markers will not be financially disadvantaged."
But The TESS has learned of growing disquiet as the implications emerge. One marker said it was no longer worth doing as much SQA work and that most people would be worse off following the removal of the general fee.
That view is supported by simple arithmetic. The general fee gave markers an additional sum of 50 times the script fee: marking 100 papers would earn 150 times the script fee, 200 papers led to 250 times the script fee, and so on.
A script fee would need to have risen by 50 per cent - few have done so - if someone marking 100 scripts were to earn the same as last year, or by 25 per cent for those marking 200 scripts.
The result is that, while exam markers will receive less for 66 papers whose script rates have fallen, many markers of the 197 papers whose rates have increased will also see their fee income drop.
There appears to be a fairly healthy rise in the rate for English Higher close reading, for example, from pound;2.64 to pound;3.56. But a marker who took on 100 scripts last year would have been paid pound;396 (150xpound;2.64). This year, payment goes down to pound;356.
In subjects where the script fee has fallen, the loss of the general fee hits even harder: 100 scripts for Standard grade business management, at Foundation level, earns pound;142 - down from pound;337.50 last year.
The SQA said 83 people had pulled out of marking as a result of the new payment structure, but it is unclear whether they knew about the general fee's removal.
The same applies to around 25 markers who expressed concerns to either the Scottish Secondary Teachers' Association or the Educational Institute of Scotland.