What payment schedule feels fair for window replacement?

I’m trying to compare payment schedules for a window replacement project, specifically whether milestone payments give the homeowner better protection than making a large deposit upfront.

One structure I’m considering is:

- 25% deposit when the contract is signed
- 25% when the windows are delivered and inspected for obvious damage
- 40% after installation is complete and the permit inspection, if required, has passed
- 10% after the punch list is finished, cleanup is complete, and the contractor provides the final invoice and warranty paperwork

Does that seem reasonably balanced, or is 25% too high before delivery? I’m also unsure whether delivery should trigger a payment at all, since the windows may be custom-ordered and could be difficult to return, but they still aren’t installed yet.

For those who have recently hired window installers, what milestones did your contract use? Did it clearly address:

- Who is responsible for permit fees and scheduling inspections?
- Whether damaged or incorrect windows must be replaced before the next payment?
- Interior and exterior cleanup, debris removal, and repairing installation damage?
- A final punch-list deadline?
- When warranty paperwork and maintenance instructions are provided?

I don’t want to withhold a legitimate final payment over minor cosmetic issues, but I also want enough unpaid balance left to encourage the contractor to finish trim, cleanup, inspection corrections, and documentation. What deposit and installment percentages have worked well in practice, and what wording helped prevent payment disputes?