Window replacement estimates look simple — so many units, so much installation — until half the work turns out to happen after the window is in: reveals, sills and making good.
Sections
Removal of old units and sills with disposal; installation counted per unit with sizes stated; the installation joint with foam plus vapour control tape inside and diffusion-open tape outside; internal and external sills separately; reveal finishing inside and out as its own line; ironmongery and adjustment; and access — working at height, lifts or scaffolding.
Reveal finishing is the most forgotten line. If it is not included, say so under exclusions rather than arguing once the reveals are open.
Also commonly missed
Hauling away old units, dust protection indoors, rehanging blinds, balcony access, and the ventilation change that follows new windows — worth a note so condensation is not blamed on the installation.
See the facade works estimate if insulation is involved.