The mistakes that actually get noticed

You do not need perfect grammar. You need to avoid the small number of errors that make a reader stop and form an opinion.

Articles. The commonest difficulty for Urdu and Punjabi speakers, because Urdu has no direct equivalent of "the". Use "a" or "an" the first time something is mentioned and "the" when the reader already knows which one. "I met a client today. The client wants a discount." Uncountable things take no article: information, advice, equipment, furniture, software.

Subject and verb agreement. One thing takes a singular verb. This goes wrong most often when words separate the subject from the verb: "the list of items is ready", not "are", because the list is what is ready.

Tense consistency. Pick a tense and stay in it. Switching between past and present within a paragraph is one of the clearest markers of a hurried writer.

Prepositions, which follow no rule and must be learned as fixed phrases: depends on, consists of, responsible for, good at, interested in, arrive at a place, arrive in a city.

Plurals with numbers. "Five year experience" is very common here and reads as an error. "Five years of experience."

Capitals. Days, months, countries, languages and names take capitals. Job titles and subjects generally do not.

Apostrophes. Possession takes one, plurals do not. "The company's policy" and "three companies". "Its" means belonging to it; "it's" means it is.