Answered by Shaykh Faraz Rabbani
Question: One of my friends doesn’t know how to recite the tashahhud. What can she do in her prayer as she doesn’t want to leave prayer? She is trying to memorize it.
Answer: Walaikum assalam wa rahmatullahi wa barakatuh,
I pray this finds you in the best of health and spirits.
Reciting the tashahhud is necessary (wajib), both in the first sitting (after two rakats) and in the final sitting (at the end of the prayer)–but not obligatory (fard). Omitting it doesn’t invalidate the prayer, but does make it deficient.
When a necessary (wajib) action is left forgetfully, forgetfulness prostrations are necessary–but not when a necessary action is left deliberately. [Shurunbulali, Maraqi al-Falah; Ala’ al-Din Abidin, al-Hadiyya al-`Ala’iyya]
In your friend’s case, she needs to:
 Take the immediate, reasonable means of memorizing the tashahhud;
 Sit for the extent of the tashahhud, repeating some invocations (such as Subhan Allah, Alhamdulillah, La ilaha illa’l Llah, wa’l Llahu Akbar).
No forgetfulness prostrations are required, nor does she have to make up or repeat such prayers.
Can New Muslims Recite from a Copy of the Qur’an During Prayer?
And Allah alone gives success.