Prepare project bids

We have to assemble the bid for the Greenfield irrigation project with cost estimates and timeline. Use the bid spreadsheet with the client contact list, confirm the unit rates for pipe and labor from the April supplier quote, enter quantities, calculate subtotal, add contingency at 8%, include the three-week lead time for specialty valves, and produce a single-sheet summary to attach to the proposal packet for the procurement review meeting on Thursday.

Before sending the bid to Procurement, make the numbers easy to approve. Put the total project price and the largest three cost drivers at the top, show where the 8% contingency is applied, flag any line items that exceed last bid by more than 10% and explain why, and add a one-line risk note about the valve lead time and its procurement impact.

I changed the April quote rates to reflect a revised supplier email and the project total shot up by 12% overnight. I checked the line rates and quantities; they seem correct but I can't tell if a hidden column or a multiplier was altered. I'm uneasy about sending this to procurement without explaining the jump. What is the most likely cause and the fastest steps to verify and document whether the change is legitimate or a spreadsheet error?

We waste days chasing revised unit rates and rechecking formulas before each bid goes to procurement, which costs credibility and time. What practical spreadsheet habits and a simple checklist will stop our team from rebuilding bids at the last minute and make approvals predictable?