There are common exclusions on most income protection plans, including;
Disability due to, or caused by, HIV/AIDS
Normal pregnancy and childbirth
Misuse of alcohol or drugs
Failure to follow medical advice
Residing outside the UK
You may not be able to make a claim for an illness you already have or have had before. Make sure you check this before you take out the policy. This will be called a pre-existing medical condition and can include any medical conditions you have, even if they haven't troubled you for a while.
Stress or back complaints, and possibly other conditions such as depression or other mental conditions , may not be covered, even if you can't work because of them. Again, it's worth checking before you take out the policy.
Unemployment cover limitations
Any income protection plans covering unemployment/ redundancy have limitations. There is usually, for those taking out a new policy, an initial exclusion period before you are eligible to receive benefits. This always applies to redundancy cover only and is typically around 90 days. Against that, you may be entitled to three months' notice before being made redundant anyway.
The unemployment/redundancy section of such a policy may be a waste of money for the self-employed as the self-employed cannot make themselves unemployed or redundant.
If you have any hand in making yourself unemployed, cover does not apply.
Contract workers on short-term contracts are not covered for end of contract.
Seasonal/ casual work is not protected by income protection plans.