Cost estimation tools can help grasp an unknown budget, and potential changes, such as new requirements or design changes, should be incorporated. Most importantly, having a well-defined project with detailed tasks will more accurately determine the required budget, rather than relying solely on data from a previous project to put together a broad estimate quickly. A work breakdown structure, along with resource details, historical data, and team members' knowledge, is used to build a stronger cost estimate. Team members who are knowledgeable about the industry and its potential risks will allocate a budget for likely changes and factor in higher costs to account for the unpredictability. Lastly, the team should revisit the cost estimate as the project progresses to reflect regulatory or resource challenges and design changes.  

Building on the point about revisiting cost estimates as the project progresses, it's worth highlighting that in the medical device space specifically, PMs can leverage a risk-based contingency framework to navigate budget uncertainty more strategically rather than reactively. Since medical device projects are governed by standards like ISO 14971 (risk management) and FDA design control requirements under 21 CFR Part 820, a PM already has a structured risk register as part of compliance obligations. This existing artifact can be dual-purposed, not just for patient safety risk mitigation, but also as a financial risk prioritization tool. By mapping each identified risk to a potential cost impact and probability of occurrence, a PM can make a more defensible case to stakeholders for contingency budget allocation, even when the full budget picture isn't initially transparent. This also ties into change control processes, which are mandatory in regulated medical device development. Every design change requires documented justification anyway, so PMs can use that paper trail to demonstrate to budget holders why additional funding is warranted, framing it not as a scope creep issue, but as a regulatory compliance necessity, which tends to carry more weight with leadership and can unlock reserved contingency funds that might not be visible to the PM at the project's outset.

Sami's point on leveraging change control documentation for budget justification is a great point that I want to delve further into. PMs in the medical device development industry can take this a step further by integrating tools such as 'Earned Value Management' (EVM) into their change control workflow to create for quantitative data for budget holders. EVM metrics such as Cost Performance Index and Schedule Performance Index give PMS real time visibility into whether the project is over or under budget relative to work completed. When a new regulatory requirement or design change arises, a PM can use current CPI trends to model project cost impacts that the change would have on the project along with the mandatory change control documentation. This changes conversations about project budgeting to actual data driven impact of a regulatory driven change on cost baselines by performance data and indicators. 
This approach also reinforces Sami's point about framing budget requests as compliance necessities. Under 21 CFR Part 820 and ISO 13485, design changes must be evaluated for their effect on the overall device, which means the documentation burden already exists. By attaching cost impact projections to that process, PMs create a feedback loop between technical compliance and financial planning that is both auditable and persuasive to stakeholders who control contingency reserves. 

One way a PM is able to navigate an unknown budget is by integrating changes that are centered on structured prioritization, phased decision-making and proactive escalation instead of waiting for a full budget before executing. If new regulatory requirements or changes do arise, a PM should assess whether the change is vital for compliance, safety or if it's just for discretion, since not all changes have the same urgency. Compliance driven changes might need immediate action, while low-priority changes might be deferred or moved to a later phase of the project. Therefore, a team can continue to move forward even when constraints are not predictable. At the same time, a PM should adjust control documentation and risk assessment and have updated cost impact estimates to communicate the consequences of action to informed funding decisions. A perspective that can be explored is that although budgets can be uncertain, a PM may need to manage requirement prioritization, not just the cost estimation. In highly regulated industries like medical devices, usually unknown budgets make it worthwhile to balance the trade offs rather than assume every change must be funded. Changing perspective to facilitating minimum changes needed to be compliant rather than focusing on enhancements can make decisions more actionable. Therefore, when budget conflicts arise from requirements, what's vital is to prioritize the requirements before assuming a budget must increase.

I really like the focus on prioritization and balancing compliance vs. discretionary changes. One additional angle that could help with unknown budgets is incremental funding or stage-gate budgeting. Instead of trying to estimate and secure a full budget upfront, PMs can structure projects so that funding is released in phases based on milestone outcomes. This allows teams to reassess costs and risks at each stage before committing further resources. This approach could work especially well in regulated environments, where new requirements often emerge mid-project. It also creates natural checkpoints to re-evaluate whether certain changes are still necessary or if alternative, lower-cost solutions exist. In a way, it shifts the mindset to adapting and justifying continuously, which might reduce the pressure of uncertainty while still maintaining control over costs.

One way a project manager can handle an unknown budget is by setting aside a contingency reserve for risks and potential design changes. Even if the budget is unknown to the project manager, the PM would usually have rough estimates or a range to work with. This would help guide how much contingency to set aside and would allow for flexibility when changes arise later. Another approach a PM could use is phased planning where cost estimates can be refined as the project progresses. This would allow a project manager to make more accurate estimates and decisions over time, instead of only relying on uncertain early estimates. It is also important for the PM to look for trade-offs between scope, time and cost. For example, if a change to the project increases cost, the PM may need to balance this by adjusting the schedule or cutting back on lower priority work. Overall, navigating an unknown budget comes down to staying flexible and continuously updating estimates as a project progresses.