Milestone

Upwork describes a milestone as "a way to divide a fixed-price contract into smaller chunks". Each one names a part of the work and a set payment. When the freelancer submits that part and the client approves it, the payment for it is released and the next milestone can start. Some contracts have only one milestone; the number is for the two sides to agree.

The mechanics that protect the freelancer sit on the milestone, not on the contract:

• Funding. The client deposits the milestone's amount before work on it begins. A milestone that was never funded is not protected.
• Submission. Work is delivered with Submit work, from Deliver work and then Your active contracts. That starts the review period: the client has 14 days to approve the work or request changes, and if they don't respond the funds are released to the freelancer automatically.
• Delivery channel. Upwork warns against delivering final work only through Messages, because then the 14-day review period never begins.

Breaking a large project into several smaller milestones is Upwork's own advice. For a freelancer it limits how much unpaid work is ever exposed at once; for a client it turns one large approval into a series of small ones. A change of scope belongs in a new or edited milestone before the work starts, not in a conversation after it is delivered.

For how the funded amount is held and what happens when a client will not pay, see escrow, Fixed-Price Protection and dispute.