Your formula exists but it’s not doing what it should. Maybe the emulsion keeps breaking. Maybe the texture went from “luxury serum” to “slightly unsettling gel” somewhere between batch three and batch four. Maybe your preservative system failed challenge testing and your manufacturer is asking questions you can’t answer. Maybe an ingredient you’ve relied on for years just got restricted in the EU and you need an alternative that performs the same way (good luck finding one without help, honestly). Maybe the product is fine but you know it could be better, and “fine” isn’t the standard you want your brand associated with.
Reformulation is for products that already exist but need professional reworking. Not starting from scratch (that’s Custom Formulation Development). Not just getting a second opinion (that’s Formulation Review). Reformulation is the middle ground: you have a formula, it needs to change, and you need someone who understands the science well enough to change it without breaking everything else in the process.