Defensibility begins with the arguments that made in the SR&ED technical report for each project claimed. 

One of the most common causes for drawn-out SR&ED claim reviews that yield a significant expenditure reduction is when a claimant/consultant prepares a SR&ED technical report that is lacking in precision, clarity and level of detail.    

These three qualities, in the SR&ED Technical Report, are the strongest predictors of successful (and defensible) SR&ED claims - even in an environment where the CRA is narrowing their interpretation of the SR&ED legislation.

After ensuring that these qualities are present in the SR&ED Technical Report, adequate preparation for a Technical Review is the second most important step that a claimant must take to ensure defensibility of their SR&ED claim.   While it is difficult to present an exhaustive set of the type of documentation considered adequate for a review, the most critical pieces are documents which capture the experimental trial details.   

While the CRA is increasingly requiring that clients have SR&ED-specific documentation prepared, there are other types of documents that evidence eligible SR&ED work.   These include Non-Conformity Reports, Red-line engineering drawings, Quality Control reports, emails with customers (discussing problems experienced), etc.