These phrases seem to cause no end of trouble!

Base on

Mistakes with this arise from incorrectly translating the Polish verb opierać. Look at the example below:

Klimatolodzy opierają się na symulacjach tworzonych na komputerach.

You CANNOT translate this as:

Climatologists base on computer simulations.

This makes absolutely no sense. Instead, the sentence should be translated as follows:

 Climatologists use computer simulations.

Climatologists depend on / rely on computer simulations in order to do their work.

If you use “base on” you must say WHAT climatologists base on computer simulations:

E.g. Climatologists base their predictions about climate change on computer simulations.

This is because the verb “base on” requires two objects (it is what grammarians call a ditransitive verb). In the above example, computer simulations is one object, and their predictions about climate change is the other.

It is sometimes difficult for a reader to understand a sentence if “base on” is used incorrectly because, as you see from the above example, they may think that some information is missing.

Some more examples:

WRONG
We solely based on information provided by Mr Andreas Schmitt in his e-mail of last Friday.
RIGHT
We based our analysis solely on information provided by Mr Andreas Schmitt in his e-mail of last Friday.

WRONG
As requested, we based on the Company’s global template employment contract for L2/L3 level employees when drafting the contract for Mr Kowalski.
RIGHT
As requested, we based Mr Kowalski’s contract on the Company’s global template employment contract for L2/L3 level employees.

WRONG
As agreed we have based on the German retention letter; however, as you will see it required significant modifications.
RIGHT
As agreed we have based the new retention letter on the German letter; however, as you will see it required significant modifications.

Based on

You can also say that “something is based on something” – this is the passive.

WRONG
It cannot be said that the actions of Top Polska S.A. base on the consumer’s ignorance or lack of experience.
RIGHT
It cannot be said that the actions of Top Polska S.A. are based on the consumer’s ignorance or lack of experience.

WRONG
Any actions that base on a consumer’s ignorance or lack of experience contradict the rules of good practice.
RIGHT
Any actions that are based on a consumer’s ignorance or lack of experience contradict the rules of good practice.
OR
Any actions based on a consumer’s ignorance or lack of experience contradict the rules of good practice.

 W oparciu o / Opierając się na

W oparciu o / Opierając się na can be translated as “on the basis of” or “based on”.

There is no such phrase as “on the base of”.

WRONG
For the purposes of this agreement “Employee” also means a person acting for the company on the base of a freelance agreement, agency agreement or other civil law contract.
RIGHT
For the purposes of this agreement “Employee” also means a person acting for the company on the basis of a freelance agreement, agency agreement or other civil law contract.

There is no such phrase as “basing on”.

WRONG
Basing on the documentation you sent us, we believe your claim has a good chance of success.
RIGHT
Based on / On the basis of the documentation you sent us, we believe your claim has a good chance of success.