These occur when outside issues affect, or are perceived to affect, the neutrality or objectivity of research. This can happen at any stage in the research cycle, including during the experimentation phase, while a manuscript is being written, or during the process of turning a manuscript into a published article.
Conflicts of interest do not always stop work from being published or prevent someone from being involved in the review process. However, they must be declared. A clear declaration of all possible conflicts – whether they actually had an influence or not – allows others to make informed decisions about the work and its review process.
If conflicts of interest are found after publication, this may be embarrassing for the authors, the Editor and the journal. It may be necessary to publish a corrigendum or reassess the review process.
Some common conflicts include:

• Personal – a pre-existing relationship induces an individual to act inappropriately.
• Financial – an individual receives payment relating to the subject of the research, or from connected organizations.
• Intellectual property – an individual puts undue emphasis on patents or trademarks that they own, or are owned by their organization.
• Affiliations – an individual is employed by, or is a member of, an organization with an interest in the outcome of the research.
• Ideology – an individual is influenced by beliefs or associations relating to the subject of the research.

You should carefully consider how these and other similar topics may affect you, and how they could affect others involved in the handling of the manuscript.