I often see the literal translation of this phrase – not later than within. This is always wrong.

Here’s an example:

POLISH
Płatności należy dokonać nie później niż w ciągu pięciu dni od daty otrzymania niniejszego pisma.

WRONG
The payment must be made no later than within five days from the date of receipt of this letter.

RIGHT
1. The payment must be made no later than five days after the date of receipt of this letter.
2. The payment must be made within five days of the date of receipt of this letter.

“Not / no later than” can only be used to refer to a point in time. So sentence 1 above refers to a day five days after the date of receipt of the letter.

“Within” can only be used to refer to a period of time. So sentence 2 refers to the period of five days that starts on the date of receipt of the letter.

You simply cannot say “no later than within” – in English. You cannot mix periods of time with points in time. It is logically incorrect.

And I wonder – is nie później niż w ciągu actually correct in Polish? Isn’t it logically incorrect in Polish too? Why not use the phrase below instead?

Płatności należy dokonać w ciągu pięciu dni od daty otrzymania niniejszego pisma.

Here are some more examples with their correct translations.

Note the patterns “no later than … after” and “within … of”.

Posiedzenie komitetu zostanie zwołane nie później niż w ciągu pierwszego półrocza 2018 roku.
The committee meeting must be held within the first half of 2018.

Zawiadomienia dokonuje się nie później niż w ciągu trzydziestu dni od daty wydania decyzji.
The notification must be made within 30 days of the date of the decision.
The notification must be made no later than 30 days after the date of the decision.

W każdym przypadku, pierwszej odpowiedzi należy udzielić nie później niż w ciągu 15 dni roboczych od otrzymania zapytania.
In any case, the first answer should be provided no later than 15 working days after receipt of the inquiry.
In any case, the first answer should be provided within 15 working days of receipt of the inquiry.

Pierwszy wlew dożylny jest podawany jak najszybciej po zdarzeniu, nie później niż w ciągu 6 godzin.
The first intravenous infusion is given as soon as possible after the incident, and no later than 6 hours after it happened.

Środki na rzecz wycofania z rynku wchodzą w życie bezzwłocznie i są wdrażane jak najszybciej, jednak nie później niż w ciągu dwóch tygodni od stwierdzenia problemu dotyczącego zgodności.
The withdrawal measures come into force without delay and must be implemented as soon as possible, and in any event not later than two weeks after the compliance problem has been identified.