A studio asks for a deposit because it is holding a place in its schedule for you and doing paid work before you can see any of it. The payment schedule is the other half of the arrangement: it keeps what you have paid roughly level with what you have received. That is the whole logic of a design agency deposit and payment schedule. Most arguments about it come from forgetting one side.
Start with what the deposit buys. While a studio is committed to your project, it is turning down other work. It also spends the first stretch on discovery and early design, which produces nothing a client can point at yet. One web design guide says reputable studios don't work entirely on spec, so a studio asking for nothing up front is the odd one out. A deposit also shows both sides mean it. It's typically non-refundable, because a held calendar slot can't be resold.
How big should it be? Published guides land in the same area. One agency contract guide calls 25 to 50 percent of the total standard practice. Another says a typical deposit runs between a quarter and a half. A third, aimed at agencies, suggests 20 to 50 percent and says smaller, shorter projects warrant a bigger share up front. A small job has little room to spread the risk, so more of it is paid early. As an example only, on a hypothetical 12,000 build, a 30 percent deposit is 3,600. If a quote sits well outside those ranges, either way, ask why.
The rest of the schedule should hang on deliverables, not dates. A date-based schedule lets feedback drag while the project is technically on time, and the studio carries the cost of the wait. A payment tied to something specific, such as approval of the design direction, a finished build, or launch, keeps everyone moving. It also means you are always paying for something you can see.
Be careful with a plain half-and-half split. It looks fair, and on a small job it usually is fair. On a larger one, an agency guide warns that it leaves the studio exposed when the final sign-off is delayed after most of the work is done. Splits such as 30/40/30 or 50/25/25 spread that exposure, and they spread yours too: you pay in steps, after each step has shown up.
The last payment deserves the most attention. It is better tied to your written acceptance of the finished site than to a number of days after delivery. A short review window, checked against the agreed scope, gives you time to test properly and gives the studio a clear point at which the work counts as done. Without one, either side can end up waiting on the other with nothing in writing that says who is late.
A schedule also protects the pace of the work. Many studios will not book a kickoff until the deposit has landed, and it is normal for work to pause if an invoice goes unpaid. That isn't a threat. It keeps money and progress level, and a late payment stops the clock on your side as well as theirs.
Before you agree to anything, ask for the schedule as amounts against named deliverables, with what triggers each invoice written beside it. If a studio can show you that in a few lines, you know what you are paying for at every step. If it cannot, that tells you more about the project than the total does.