When a potential employer determines a candidate's salary, will he only take the basic pay into consideration or fixed allowances as well?

For eg. A bank ops analyst who works the London shift gets $3k basic and $1k fixed allowance per mth and receives 5 mths bonus for the year.

When he subsequently interviews with another bank to do normal hours (9-6pm type), will the new employer consider the candidate's last drawn as $4k and offer him a pay above $4k, or will the employer ignore the $1k allowance and offer the candidate a % above $3k?

HR will not take the 5 mths bonus into consideration rite? Since it's variable and not a sales position.

Any experts to share?