Error carried forward.
The rule that stops one slipped decimal in step two costing a student the whole question. Almost nobody applies it consistently at eleven at night on the fortieth paper.
In one line: error carried forward means a student who makes a numerical mistake early in a multi-step answer still earns the marks for every later step they work correctly from that wrong value. They are penalised once, not all the way down.
What it actually says
If a student makes an error early in a multi-step answer, and then carries that wrong value correctly through the remaining steps, the later steps still earn their marks. The student is penalised once, for the mistake they made, and not repeatedly for the consequences of it.
A three-mark numerical is a mark for the correct approach, a mark for correct substitution, a mark for the arithmetic. A student who writes the right formula, substitutes correctly, and then divides wrongly has earned two of the three. Marking that answer zero because the final number is wrong is not strictness — it is a misapplication of the scheme.
Where it applies
- Numericals in Physics, Chemistry and Mathematics, which is the obvious case.
- Derivations, where a wrong intermediate expression is carried through correctly to the end.
- Accountancy and Economics, where a wrong figure in one statement flows into the next and the treatment is still right.
- Multi-part questions where part (b) uses the answer from part (a).
Where it does not
It is not a general amnesty. A wrong formula is a wrong method, not a carried error. If the mistake is conceptual rather than arithmetical, the marks for the concept are gone — the student has not demonstrated the thing the mark was for. The distinction is between “knew what to do and miscalculated” and “did not know what to do”.
What it is worth, in marks
The amount at stake is set by how the question splits, not by the size of the mistake. On a three-mark numerical the split is usually one mark for the method, one for correct substitution and one for the final value. A student who slips in the arithmetic loses the third mark. Marked without the convention, they lose all three.
| Step | What the student wrote | With the convention | Without it |
|---|---|---|---|
| Formula | Correct | 1 | 0 |
| Substitution | Correct | 1 | 0 |
| Arithmetic | Slipped a decimal | 0 | 0 |
| Out of 3 | 2 | 0 |
Across a paper with six or seven numericals that is the difference between a student who understood the method reading 70 and reading 48. It is the most expensive marking error there is, and it is invisible to anyone checking only the final answers.
Why it is so inconsistently applied
Because applying it properly means reading every step of every answer, including the answers that reached the wrong total. The temptation, on a large pile, is to check the final value against the key and move on. That is faster, and it systematically punishes the students who understood the method.
It is also the single most common reason a parent arrives at a centre holding a paper and asking why their child got nothing for an answer that is visibly almost right. They are usually correct.
The consistency problem is the real one. Most teachers apply error carried forward correctly on paper one and progressively less carefully by paper forty — not through carelessness, but because it is genuinely tiring to trace a wrong value through four steps, two hundred times.
What to do about it
If you are marking by hand: mark question-wise rather than paper-wise. Doing all forty copies of question 3 in a row holds the standard far better than doing all thirty-three questions of one paper before starting the next.
If you are using software to help, this is the specific thing to test it on. Take a paper where a student got an early value wrong and carried it through. If the tool zeroes the question, it is matching final answers against a key, and it will do that to your students every week. Our note on where AI checking should and should not be trusted has the other tests worth running. For definitions, see the rest of the marking vocabulary.
What CBSE actually tells its examiners
The principle is not folklore, but it is thinner in writing than most people assume. CBSE's general instructions to examiners carry one line bearing on it: an error is not to be deducted for its cumulative effect, and is to be penalised only once.
Be precise about what that does and does not say, because the difference decides marks. It says the mistake is charged once, where it happened. It does not say the later steps are then credited from the student’s own wrong value — CBSE publishes no mark-by-mark follow-through rule, and the phrase “carried forward” does not appear in its schemes at all. Several other Indian boards publish no examiner instructions on the point whatsoever. So the convention described on this page is what a careful examiner does with that instruction, not a rule quoted from one. The gap between the two is the whole problem.
Where this bites hardest
Physics, because a numerical answer there is built from a chain of steps and a single arithmetic slip sits in the middle of it. How the marks are split across a Class 12 Physics derivation works through where error carried forward does and does not rescue a wrong final value. The term is also written follow-through marks, chiefly in IB and Cambridge schemes; it means the same thing.
Questions people ask about it
What is error carried forward?
A marking convention. When an answer has several steps and the student makes an error in one of them, the steps after it are marked on whether they follow correctly from the wrong value — not on whether they reach the right final answer. The mistake costs its own mark and nothing more.
What does error carried forward mean in practice?
That an examiner has to read the working, not just the result. If the method is right and the student has carried their own wrong number through it consistently, those steps earn full credit. If the student abandoned the method or changed approach halfway, they do not.
Is error carry forward the same thing?
Yes. “Error carry forward”, “error carried forward” and the abbreviation ECF all describe the same convention. The wording varies between marking schemes; the rule does not.
Does it apply to a wrong formula?
No. A wrong formula is a wrong method, and the marks for the method were never earned. The convention protects a student who knew what to do and miscalculated, not one who did not know what to do. That line is the whole judgement, and it is where two examiners most often disagree.
See it on your own paper.
Send us one you have already marked, including the answers where a student slipped early. Compare what comes back. The first paper is free.