A Phase II proposal is not a longer version of your Phase I proposal. Phase I asked whether the idea could work. Phase II asks whether you can build it, whether your team can execute a multi-year development effort, and whether anyone will buy the result. Reviewers who liked your Phase I concept read the Phase II submission with a different set of questions in mind, and strong technical writing alone does not carry it.
Phase I results are evidence, not decoration
Everything in a Phase II proposal should trace back to what Phase I actually produced. Reviewers want the measured data, the test conditions, and the specific technical risks the feasibility work retired. Vague claims that the concept "was validated" invite skepticism. The strongest proposals show the numbers, name what is still unknown, and explain how the Phase II plan attacks exactly those gaps. The structural differences between the phases are covered in our comparison of Phase I and Phase II.
A development plan, not another feasibility study
Phase I plans are exploratory. Phase II plans have to read like engineering project management: tasks with owners, dependencies between them, decision points where you would change course, and deliverables a program officer can verify. Agencies vary in how formally they want this presented, but every panel is judging whether the schedule is achievable rather than aspirational. Padding a plan with optimistic parallel tasks is a reliable way to lose credibility. Read our guidance on milestones and reporting before you write the schedule, because the milestones you propose become the ones you are held to.
Commercialization carries far more weight
In Phase I the commercial section is often a short statement of intent. In Phase II it is a scored component, and at some agencies it is weighted close to technical merit. Reviewers look for named customer types, evidence you have spoken to them, a realistic path to revenue, and an honest read on what production will cost. Letters of interest from potential buyers or integrators help considerably. Write the section as if an investor were reading it, then check it against our detailed treatment of the commercialization plan.
Team, budget, and an awkward Phase I result
Phase II budgets are large enough that reviewers scrutinize them line by line. Named personnel with real time commitments beat placeholder roles. Subcontractors and consultants have to be justified, and the share of work performed by your own company is constrained by program rules that differ between SBIR and STTR. Confirm the current cost principles and any statutory work-share minimums with your agency and your accountant before you submit; this is general information, not accounting advice.
If Phase I underdelivered, address it directly. Panels almost always spot a buried failure, and a candid account of what went wrong, what you learned, and how the plan changed reads far better than silence. Some agencies also run demonstration and pilot programs that can supplement a Phase II effort, so ask your program officer what else is on the table.
Projects House supports Phase II applicants on the engineering side of the proposal: development plans, risk analysis, and cost estimates that hold up under review. Send us your Phase I results through the contact form.