• Gain the potential to scribe scrolls at 9th level (PHB p. 43 / DMG p. 117)
• Must have their spell book at hand to guide their work (DMG p. 119)

• Gain the potential to scribe scrolls at 7th level (DMG p. 117)
• Must work on a specially prepared altar (DMG p. 119)

The spellcaster knows the basics of the art and has learned where to look for the information he needs to make the attempt. The exact process for each spell is still a mystery to him. He may consult a sage, seek the guidance of a higher level spellcaster, or even use spells to call upon greater powers. (DMG p.117-119)

• Scrolls always has a casting level (for determining level-based variables such as range, damage, duration, and resistance to dispel attempts) of one level higher than the minimum required to cast it, but never less than 6th level. In other words, the act of writing a scroll limits its power. (DMG p. 196)
• The DM can allow characters to control the casting level of scrolls they scribe, so long as it is not less than the minimum level required to cast the spell. (Sage Advice #248 p. 20+22)