Choose the correct preposition to complete the sentences. You may want to read the comments below the exercise first.


1.  The contractor must complete the construction by until (1 p.) the agreed deadline of 31st December.

2.  The warranty is valid by until (1 p.) the end of the calendar year following the purchase date.

3.  The tenant may occupy the property by until (1 p.) 30th June, after which the lease will terminate.

4.  The supplier shall deliver the goods by until (1 p.) 15th March 2024.

5.  The buyer is required to make the final payment by until (1 p.) the date of completion.

6.  The confidentiality obligation shall continue by until (1 p.) the information becomes publicly available.

7.  The parties agree to exchange all necessary documents by until (1 p.) close of business on the specified date.

8.  This agreement shall remain in force by until (1 p.) terminated by mutual consent.

9.  The tenant must pay the rent by until (1 p.) the 5th day of each month.

10.  The seller retains ownership of the goods by until (1 p.) full payment has been made.

by
The payment must be done by the 20th day of every month.
Explanation: "By" sets a deadline. The action (payment) must be completed before or on the 20th day. It is used to indicate a fixed point in time by which something needs to happen.

until
The agreement is valid until 20th October.
Explanation: "Until" shows the period of time up to a specific point. In this case, the agreement remains valid through the 19th and ends on the 20th October.

Quick Rule of Thumb
Use "by" when referring to a deadline for an action to be completed.
Use "until" when referring to the duration or continuation of a state, condition, or activity.

Mnemonic Device
By = Before or on (a deadline).
Until = Up to (a time when something stops).