Rehearsal dinner

We are having one the night before and inviting our wedding party, their significant others, our parents and anyone who came from out of province. Most of our wedding guests are coming from out of town so we couldn’t accommodate all of them at the dinner. We are paying for everyone’s dinner but it is just a buffet dinner. The room rental for the rehearsal dinner is included in the cost of renting our ceremony space. Also if we have more than 15 people (which we would with our wedding party alone) then the bride and groom eat free for the night

For my wedding, we (us and all of our guests) are actually staying at the venue for 2 nights. We will be having a rehearsal type BBQ on the day of everyones arrival. It'll be a fun time to just relax and chill before the wedding.

I think the rule of thumb for a rehearsal dinner is to invite bridal party, parents, siblings, and out-of-town guests.

As already mentioned, invite parents, sibling, wedding party, anyone with a role in the wedding. Out of town guests that have arrived the day before can definitely be invited, but it's not mandatory to invite them.

More often now, brides and grooms are paying for the wedding. The bride's parents used to pay more back in the day but it's not as customary now. Parents can definitely still help pay for things (i.e. the dress, the bar, etc) but many don't pay for the whole affair nowadays.

Invite - up to you, but for rehearsals it's usually immediate family and those in the wedding (like others have stated) Since it isn't a rehearsal though - feel free to invite out of town guests too, but you don't want to have it where you are basically inviting everybody that will be attending the wedding.

Pay for wedding - that is usually the Bride and Groom nowadays but back in the old times it was the Brides family

Pay for the rehearsal - that is usually everybody paying for themselves but back in the old times it was the Grooms family

As everyone else has said, immediate family, bridal party and out of town guests depending on how many you have.

We are just doing immediate family (siblings are all in the wedding party) so it would only be about 20 people

Traditionally, the rehearsal dinner is hosted/paid for by the groom's parents. Guests typically include the immediate family, wedding party, officiant and OOT guests (though that last one is very much optional!).

It can be as laid back or formal as you'd like. Nowadays, couples often host this dinner 1-2 days before the wedding, so that everyone can have a chill and early night the day before the wedding! You also don't need to come up with a "theme" like a shower or bachelorette party, unless you want to!

Since you are not having an actual rehearsal, i would include immediate family, the bridal party and your out of town guests. As for paying for the wedding I think it is more common for the bride and groom to pay for it. Parents of the bride and groom may contribute if they are able.

Usually immediate family and whoever is “involved”, I.e. bridal party and any family or friends who would do a reading or take part in the ceremony.