(something) is required

When you say that something "is required", it means that people have to do it.

Things that people often say "are required" include:

• Attendance is required.
• Registration is required. (You have to register.)
• Immediate action is required. (You have to act quickly.)
• Further research is required. (This is often used at the end of academic journal articles to say that someone needs to research a topic more.)
• A permit is required. (You need a permit, which is an official document that shows you're allowed to do something.)

a non-refundable deposit

A "deposit" is some money that you pay at first when you're reserving something. You might need to pay a "deposit" in situations like:

• when renting a car
• when signing up for classes
• when renting an apartment

You can express the amount of a deposit like this:

a $400 deposit 

a 10% deposit

Sometimes a deposit is "non-refundable". This means that you can't get the deposit back after you've paid it.

(do something) at time of (booking/registration)

This formal expression comes up in written legal agreements and policies. Use "at time of" to describe when something, like a payment, will happen. For example:

First and last months' rent is due at time of signing.

Your account will be charged at time of shipping.