You can purchase extra bags at the check-in desk, but be aware that airport prices are significantly higher than online rates.
The process varies slightly depending on whether you booked directly or through a travel agent: buy extra baggage british airways
Silver and Gold members (and Oneworld equivalents) often get an additional free checked bag on most routes, regardless of fare class (excluding Basic). You can purchase extra bags at the check-in
This is the standard method. Log in to the British Airways website or mobile app with your booking reference and last name. buy extra baggage british airways
Each extra bag typically follows the standard weight limit of your cabin (usually 23kg for Economy/Premium Economy and 32kg for Business/First).
Before buying, check if your ticket already includes a checked bag: