The guest list is where budget, venue capacity and family diplomacy collide — and it's usually easier to solve early than to trim later once invitations are half-written.
Start from a hard number, not a wish list
Work backwards from what your venue and budget can actually support, then build the list against that ceiling — rather than making an aspirational list first and being disappointed when it has to shrink.
A day-guests/evening-guests split
Many Scottish weddings invite a smaller number to the ceremony and wedding breakfast, then open the evening reception (often built around a ceilidh) to a wider group of friends, colleagues and extended family. This is a well-established way to include more people without the cost of a full sit-down meal for everyone — just be clear on invitations about which parts of the day someone is invited to.
Plus-ones
A common, low-friction rule: offer a plus-one to anyone in a long-term relationship (married, engaged, living together, or a long-standing partner), and treat single friends case-by-case based on whether they'd know other guests. Whatever rule you choose, apply it consistently — inconsistent plus-one decisions cause more offence than a clear "no plus-ones for this group" policy.
Children
Decide early whether the day is child-friendly or adults-only, and say so clearly and consistently on every invitation — mixed messaging (some children invited, others not, without an obvious reason like immediate family) is one of the most common sources of guest-list friction.
Family politics
If parents are contributing financially, it's reasonable that they get a say in some invitations, but agree the split of "their" invitations early rather than leaving it open-ended. For blended families or estranged relatives, decide your approach as a couple before anyone else weighs in, and stick to it.
A working buffer
Even with confirmed RSVPs, expect a small number of late cancellations and, occasionally, late additions. Build a short waiting list rather than over-inviting from the start.