@kaloidq it depends if the reference letters used for skills assessment comply with immigration requirements.
For our clients we assist from start to finish, we most often use the same only because from the skills assessment application pa lang, we tailor the letters already to fit both assessing body and immigration requirements. However, there are those clients who we've acquired after they have had their skills assessed and upon checking the letters and evidences they used previously, we’re not satisfied that they would comply with immigration standards so we assist them in producing new letters and evidences.
So in short, make sure you review the documents again and that it fits in to immigration criteria. Good luck!