The word(s) "excuse" appears 18 time(s) in 17 verse(s) in Quran in Mohsin Khan translation.

(1) And make not Allah's (Name) an excuse in your oaths against your doing good and acting piously, and making peace among mankind. And Allah is All-Hearer, All-Knower (i.e. do not swear much and if you have sworn against doing something good then give an expiation for the oath and do good).

(2) There will then be (left) no Fitnah (excuses or statements or arguments) for them but to say: "By Allah, our Lord, we were not those who joined others in worship with Allah."

(3) Then after them succeeded an (evil) generation, which inherited the Book, but they chose (for themselves) the goods of this low life (evil pleasures of this world) saying (as an excuse): "(Everything) will be forgiven to us." And if (again) the offer of the like (evil pleasures of this world) came their way, they would (again) seize them (would commit those sins). Was not the covenant of the Book taken from them that they would not say about Allah anything but the truth? And they have studied what is in it (the Book). And the home of the Hereafter is better for those who are Al-Muttaqun (the pious - See V.2:2). Do not you then understand?

(4) Make no excuse; you disbelieved after you had believed. If We pardon some of you, We will punish others amongst you because they were Mujrimun (disbelievers, polytheists, sinners, criminals.).

(5) And those who made excuses from the bedouins came (to you, O Prophet صلى الله عليه وسلم) asking your permission to exempt them (from the battle), and those who had lied to Allah and His Messenger sat at home (without asking the permission for it); a painful torment will seize those of them who disbelieve.

(6) They (the hypocrites) will present their excuses to you (Muslims), when you return to them. Say (O Muhammad صلى الله عليه وسلم) "Present no excuses, we shall not believe you. Allah has already informed us of the news concerning you. Allah and His Messenger will observe your deeds. In the end you will be brought back to the All-Knower of the unseen and the seen, then He (Allah) will inform you of what you used to do." [Tafsir At-Tabari]

(7) And what think those who invent a lie against Allah, on the Day of Resurrection? [i.e. Do they think that they will be forgiven and excused! Nay, they will have an eternal punishment in the Fire of Hell]. Truly, Allah is full of Bounty to mankind, but most of them are ungrateful.

(8) And (remember) the Day when We shall raise up from each nation a witness (their Messenger), then, those who disbelieved will not be given leave (to put forward excuses), nor will they be allowed (to return to the world) to repent and ask for Allah's Forgiveness (of their sins).

(9) [Musa (Moses)] said: "If I ask you anything after this, keep me not in your company, you have received an excuse from me."

(10) Make not the calling of the Messenger (Muhammad صلى الله عليه وسلم) among you as your calling one of another. Allah knows those of you who slip away under shelter (of some excuse without taking the permission to leave, from the Messenger (صلى الله عليه وسلم). And let those who oppose the Messenger's (Muhammad صلى الله عليه وسلم) commandment (i.e. his Sunnah - legal ways, orders, acts of worship, statements) (among the sects) beware, lest some Fitnah (disbelief, trials, afflictions, earthquakes, killing, overpowered by a tyrant) should befall them or a painful torment be inflicted on them.