Advanced assurance in R&D

Has any found the advanced assurance process straight forward to use and what have the time scales been like?
Also has anyone previously submitted R&D claims directly on CT600 that were rejected, then used the advance assurance for a subsequent year and been successful?

Hi Melissa willment
You appear to be seeking feedback from other Corporation Tax customers regarding their experience of making R&D claims.
This forum is not appropriate for questions like this.
Thank you