Mixed dentition orthodontic treatment aims to correct dental arch irregularities and abnormalities in occlusal relations, and to eliminate functional interferences. Proper management of space in the mixed dentition can prevent unnecessary loss of arch length, allowing for beneficial use of the leeway space. Invisalign First clear aligners (Align Technology, San Jose, CA, USA) are specifically designed to simplify the management of malocclusion in younger patients, who often present shorter clinical crowns, erupting dentition and dental arch expansion. The present study seeks to provide indications for successful digital planning and to describe a standardised treatment protocol for maxillary development with Invisalign First. Invisalign First aligners make it possible to treat a broad range of phase 1 orthodontic problems such as anterior crowding and spacing (mild to moderate), loss of arch length due to premature loss of primary teeth and mesial drift, constricted arches (up to edge-to-edge buccal horizontal overlap), anterior reverse articulation (usually one or two teeth), midline diastemas, mild to moderate deep bite, and flared/protruded incisors. It is also possible to treat patients with a mild Class II or Class III molar relationship by rotating and distalising the molars by ~1 mm. The clinical protocol described for phase 1 treatment with Invisalign First aligners has been designed to manage the developing occlusion, guiding the teeth into a proper maxillary arch form. The 10 steps outlined in the present study are intended to be easy to follow during digital planning to help practitioners to deliver such predictable therapies by developing the maxillary arch using clear aligners.