Seed the autoincrement differently for each office?
1 for head office
100,000,001 for 1st branch
200,000,001 for 2nd branch
2,000,000,001 for 20th branch
if you need more rows/branches than can be accomodated with int (including -ve int seeds), try bigint.
Use creatorid & id as composite primary key (and composite foreign key in related tables).