Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.

Prayers have appointed times and one must offer them at these times. Allah says: “Prayer has been ordained on the believers at their appointed times.” (Qur’an 4:103)

If for one reason or another, one failed to do so, they should do it without further delay:

The Prophet (peace be upon him) said, “Whoever could not pray because of oversleeping or forgetfulness, he should do so as soon they remember it.” (Al-Bukhari and Muslim).

There are other traditions to confirm this: Once the Prophet was seen praying after Asr, when his wife, Umm Salamah, inquired about it, he said, “I was distracted from praying the Sunnah of Zhuhr because of the people of Banu al-Qays, and so, I was making up for it.” (Al-Bukhari and Muslim)

Another report from Ibn Majah on the authority of Qays ibn Amr states, “Once the Prophet, peace be upon him, saw a man praying after Fajr; he asked him, “Are you praying Fajr twice?, he replied, “I did not pray the two rak’ahs before Fajr, and so I wanted to make it up.” On hearing this, the Prophet remained silent.”  (Ibn Majah)

If it had been forbidden, the Prophet, peace be upon him, would have said so.

Based on these traditions, the majority of scholars are of the view that the prayers one failed to do should be done without delay, even if it was one of the times when prayers are otherwise forbidden or considered undesirable.

Almighty Allah knows best.