Holiday entitlement for part-time workers is the same as for full-time workers, calculated on a pro rata basis.
Accrual: During the first year of work, workers start to accrue their holiday entitlement at the rate of 1/12th of the annual entitlement and may take it on that basis.
All full-time workers above school leaving age are entitled to 4.8 weeks (or 24 days) paid holiday per year. So you are accruing holiday leave at the rate of two days per month.
At the end of your first calendar month, you would therefore have accrued two days holiday. A worker would be entitled to apply for two days holiday leave to occur after that period of accrual.
Employee Notice: The employee is required by statute to provide sufficient notice. Regulation 15(1) of the Working Time Regulations states that notice must be issued before the relevant date.
This must be twice as many days in advance of holiday as the number of days to be taken. Which is a long way round to saying if you want to take two days holidays, you should provide notice at least four full days beforehand, unless stated otherwise in your contract.
The Employer’s rights: Even complying with the letter of the law doesn’t mean to say that the employer has to agree to the application. If the business wants to refuse the application it can serve notice on the employee. The period of notice in reply must be at least equivalent to the period of leave requested.
So, for example, one day’s notice of a refusal for two day’s leave is sufficient to comply with the employer’s right under Regulation 15(2).
The refusal can only be made on so many occasions of course, because (subject to any contractual right to carry holiday over to the next year) the employer must enable the employee to take their annual holiday leave entitlement in the year in which it accrued.
See also: Holiday leave and pay: the law