Short answer
Alterations can often adjust hems, sleeves and some areas of fit; structural changes to shoulders, collar balance or proportions may be limited or impractical. Ask the tailor to assess the garment and confirm the scope, cost and completion date before relying on it for the wedding.
What alterations can and cannot do
Can: sleeve length, waist suppression, trouser hem and break, jacket length at the margin, button stance tweaks. Cannot: shoulder structure, collar balance, blade position, the garment’s fundamental proportions — which is why the shoulders rule (buy RTW on the shoulders, alter the rest) is the first law of the alterations tailor. See the RTW guide for how far honest alteration goes.
The wedding-week calendar
Set an alteration deadline with the tailor that leaves time to inspect and try on the finished garment before the wedding. The time needed depends on the work and the tailor’s schedule. Try the full outfit with the intended shoes and shirt before the day.
Commissioning versus altering an existing suit
A new commission and alterations to an existing suit are different routes. Ask what fitting stages are included in a new order and whether any later correction is covered, chargeable or handled by a local tailor. Compare the written scope and total cost.
Planning a real wedding? The house fits grooms and their parties across Europe on the proposed 2027 programme — bring the date and the venue photographs to the first fitting, and the calendar is planned backwards from the day.