To write the Series 9/10 examination, you are required to have a Series 7 license. However, you do not have to hold the license for any certain period of time before you can write.
The 36-month requirement applies if you would like to become a branch manager for a firm. In this case, the NYSE
requires an individual to have held his or her Series 7 license for a period of at least 36 months.
For more on the Series 9/10 exam, click here