Group meals - how to factor in shared items on different bills?

Hi all!

I’ve seen a few posts on the topic of group dinners and the time of paying the bill - I’ve increasingly been having the awkward moment when everyone suggests splitting the bill among all the participants, and I will eventually say yes to that as I’ve shared a few items of the bill (usually starters or appetisers).

Although I wholeheartedly agree with the position of many on asking for separate checks when ordering my meal, how do you factor in the odd item that you do share with the rest of the table?

On a slightly different topic, why are Brits in specific so awkward about everyone paying for their own bill? And more generally, awkward about discussing money related topics?

Thanks everyone!