The complete IB Internal Assessment guide
Every IB subject includes an internally assessed component marked against published criteria: the sciences out of 24, History and Business Management out of 25, Mathematics out of 20, Economics 14 per commentary. Your teacher marks it and the IB moderates a sample, so the criteria are what count.
Internal Assessments (IAs) are a core component of every IB Diploma Programme subject. Unlike externally examined papers, IAs are completed during the course, supervised by your teacher, and then externally moderated by the IB. They usually account for 20% to 30% of the final subject grade, and more in some arts subjects (the Film portfolio is 40% at SL), which makes them one of the most controllable parts of your IB score: you have weeks or months to refine them, not a timed exam.
This guide explains how IAs work across different subject groups, what markers look for when applying the criteria, the most common mistakes students make, and concrete strategies for achieving top marks. Whether you are writing a History IA, a Biology lab report, or a Mathematics exploration, the principles of strong IA work are consistent.
What is the Internal Assessment?
The Internal Assessment is a piece of coursework completed under teacher supervision that demonstrates your ability to apply subject knowledge independently. The format varies significantly by subject:
- Group 1 (Studies in Language and Literature): the individual oral, a recorded oral on a global issue explored through an extract from each of two works (in Literature, one work originally written in the language studied and one work studied in translation; in Language and Literature, one literary work and one non-literary text)
- Group 2 (Language Acquisition): an individual oral, based on a visual stimulus at SL and an extract from a literary work at HL in Language B
- Group 3 (Individuals and Societies): a written investigation (History: 2,200 words; Business Management: 1,800 words; Economics: three commentaries of up to 800 words each; Psychology: an experimental report through November 2026, and from May 2027 a research proposal marked out of 24)
- Group 4 (Sciences): the scientific investigation (Biology, Chemistry, Physics: up to 3,000 words, marked out of 24)
- Group 5 (Mathematics): the mathematical exploration (approximately 12 to 20 pages)
- Group 6 (The Arts): varies by subject (Visual Arts: the exhibition, replaced from May 2027 by resolved artworks (SL) or selected resolved artworks (HL), which are internally assessed; Music: experimenting with music, and at HL also the contemporary music-maker; Film: the film portfolio, and at HL also the collaborative film project). The Visual Arts comparative study and the Music and Film coursework IBLens marks are externally assessed components.
Despite these format differences, IAs share common expectations: independent work, engagement with the methods of the subject, and clear communication.
How IAs differ by subject group
Understanding the specific expectations for your subject is critical. Here is a deeper look at what distinguishes IAs across the major subject groups:
Sciences (Group 4)
Science IAs ask you to design and carry out your own investigation, which can be an experiment or work with a database or simulation. The emphasis is on scientific method: a focused research question set in context, controlled variables, enough data, processing with appropriate tools, and an evaluation of the method. The criteria reward understanding why you made each methodological choice, not just what you did. A common misconception is that complex experiments score higher; in reality, a simple experiment with a rigorous method and a thoughtful evaluation often outscores an ambitious one with poor controls.
History (Group 3)
The History IA is a 2,200-word investigation into a historical question. It asks you to identify and evaluate sources (Section 1), investigate the question using evidence (Section 2), and reflect on the methods used by historians (Section 3). The Investigation carries 15 of the 25 marks, and what lifts it is evaluation of different perspectives: not only noting that historians interpret the same events differently, but weighing those interpretations to reach a reasoned conclusion.
Mathematics (Group 5)
The mathematical exploration asks you to explore a topic of your own choosing. There is no fixed structure, but the criteria look for personal engagement with the mathematics, appropriate notation and terminology, and mathematics used with understanding rather than only calculation. The strongest explorations connect the mathematics to a context that interests the student, then use mathematics at the level of the course within that context.
Economics (Group 3)
Economics requires three commentaries of up to 800 words each, based on published news articles. Each commentary must apply economic theory to explain a real-world event, use appropriate diagrams, and evaluate the economic implications. The challenge is depth of analysis within a tight word limit: every sentence has to contribute. Commentaries that describe the article without applying economic theory lose marks on application and analysis.
Assessment criteria explained
While specific criteria vary by subject, most IAs are assessed against 4-5 criteria that evaluate similar competencies:
| Competency | What the Criteria Reward | Common Weakness |
|---|---|---|
| Research Question / Focus | Clear, specific, answerable question appropriate to the subject | Too broad, too vague, or not investigable |
| Methodology / Investigation | Appropriate methods, sufficient data/evidence, controlled variables | Insufficient data, poor controls, unexplained choices |
| Knowledge & Understanding | Accurate use of subject terminology, concepts, and theories | Superficial understanding, incorrect terminology |
| Analysis & Evaluation | Critical thinking, interpretation of results, acknowledgement of limitations | Descriptive rather than analytical, ignoring anomalies |
| Communication | Clear structure, appropriate format, academic conventions | Poor organisation, missing citations, exceeding word/page limits |
Where the weight sits differs by subject. History puts 15 of its 25 marks on the Investigation, Computer Science 12 on Development, and Mathematics 6 of 20 on Use of mathematics, while the four science criteria are worth 6 marks each. What holds across subjects is that description alone keeps an IA in the middle levels: the higher levels ask you to interpret your findings, weigh their significance and acknowledge their limitations.
Common pitfalls per criterion
Issues that commonly cost marks:
Research Question: Students often choose questions that are either too broad ("How does temperature affect enzyme activity?") or too narrow ("Does the pH of my school's water fountain change between 8am and 9am on Tuesdays?"). The sweet spot is a question that allows for genuine investigation within the constraints of your resources and time.
Methodology: in the sciences, too few repeats and variables that were never identified or controlled. In the humanities, reliance on a single type of source, or sources used without being evaluated.
Analysis: The single biggest pitfall is describing rather than analysing. Stating "the graph shows an upward trend" is description. Explaining why the trend occurs, whether it matches theoretical predictions, what anomalies suggest and what the limitations of the data are: that is analysis.
Evaluation: Many students treat the evaluation as a place to list "errors" such as "human error" or "the timer was inaccurate". The criteria reward specific, realistic limitations that actually affected the results, with concrete suggestions for how the investigation could be improved if repeated.
How IAs are actually marked
Understanding the marking process helps you write for your audience. Here is how IA assessment typically works:
Your teacher marks your IA first, applying the criteria for the subject and awarding a mark out of the maximum, which ranges from 20 to 45 depending on the subject. The marks are then submitted to the IB, along with a sample of work from your school.
An external moderator appointed by the IB reviews the sample to check whether your teacher's marking matches the global standard. If the marking was too generous or too harsh, a moderation factor is applied to the marks of every student at the school for that component, up or down. This means your final IA mark may differ from what your teacher awarded.
Key implications for students:
- Your IA must explain itself: the moderator has never met you and cannot ask clarifying questions
- Clarity of communication matters enormously; if the moderator cannot follow your argument, they cannot award marks for it
- Following the prescribed structure and format for your subject makes it easier for moderators to find evidence of each criterion
- Your teacher's mark is not final, so aim for what the top levels of the criteria describe rather than only for your teacher's approval
Time management for IA
The subject guides allocate a set number of hours to the IA: 10 in the sciences, 20 in Economics, and more in some subjects, such as Computer Science. The biggest time management mistake is leaving the IA until the last few weeks before the deadline. This leads to rushed methodology, insufficient data collection, and superficial analysis.
A recommended timeline for a science IA (adaptable to other subjects):
- Weeks 1-2: Topic exploration, background research, research question formulation
- Weeks 3-4: Methodology design, preliminary trials, variable identification
- Weeks 5-7: Data collection (with sufficient repetitions and controlled conditions)
- Weeks 8-9: Data processing, graph creation, statistical analysis
- Weeks 10-11: Writing the report (introduction, methodology, results, analysis, evaluation, conclusion)
- Week 12: Revision, proofreading, formatting, teacher review
Starting early also gives you time to redo experiments if initial results are inconclusive, or to pivot your approach if your original methodology proves unworkable.
Editing and revision strategy
The difference between a good IA and an excellent one often comes down to revision. Here is a structured approach to editing your IA:
First pass: Structure and argument. Read your IA from start to finish and ask: Does every section contribute to answering the research question? Is there a logical flow from introduction to conclusion? Are there any gaps in the argument?
Second pass: Criteria alignment. Go through each criterion for your subject and highlight where in your IA you have addressed each one. If you cannot find clear evidence for a criterion, you need to add content. This is where a tool like IBLens can help: by marking your IA against the criteria for your subject, it shows which areas need strengthening before submission.
Third pass: Academic conventions. Check citations, formatting, terminology, and word/page count. Ensure all graphs have titles, axes labels, and units. Verify that your bibliography is complete and consistently formatted.
Fourth pass: Clarity and concision. Remove redundant sentences, replace vague language with specific terminology, and ensure every paragraph has a clear purpose. In subjects with tight word limits (like Economics commentaries), every word must earn its place.
For a deeper understanding of how criterion-based marking works across all IB essay types, see our IB essay criteria explained guide. If you are working on your Extended Essay alongside your IA, our Extended Essay guide covers the specific requirements for that component. For understanding how your IA mark contributes to your overall IB score, check our IB grade boundaries explainer.
Get AI feedback on your IA in a minute or two: Biology IA, Chemistry IA, Physics IA, Economics IA, History IA, Business Management IA, Mathematics IA, or Psychology IA, each marked against the criteria for that subject.