Pro-Rata Salary in Singapore: The Incomplete-Month Formula

An employee who works only part of a month is paid (monthly gross rate of pay ÷ total working days in the month) × days actually worked — the incomplete-month formula published by MOM. It applies to mid-month joiners, leavers, and no-pay leave. The trap is the denominator: it counts public holidays but not rest days, and it changes every month.

Last reviewed 10 June 2026 · Source: Ministry of Manpower.

When the incomplete-month formula applies

Use it whenever an employee on a monthly salary performs an incomplete month of work:

• Started work after the 1st of the month.
• Left employment before the last day of the month — pair this with the final-salary deadlines.
• Took no-pay leave during the month.
• Was on reservist for part of the month (NS pay claims run separately through the MINDEF portal — you pro-rate the salary, then claim the make-up pay).

Paid leave does not trigger it. An employee on annual leave, paid sick leave or a paid public holiday worked a "complete" month for salary purposes — those days are paid days.

Step 1 — Establish the gross rate of pay

The formula runs on the gross rate of pay, not basic. MOM defines gross as basic pay plus contractual allowances, and specifically excludes:

Included	Excluded
Basic salary	Overtime payments
Contractual allowances	Bonus payments and AWS
	Reimbursement of special expenses
	Productivity incentive payments
	Travel, food and housing allowances

Note the asymmetry that catches spreadsheets and payroll software alike: incomplete-month pay uses the gross rate, but overtime and rest-day rates run off the basic rate. Two different bases, one payslip.

Step 2 — Count the working days in the month

"Total number of working days in the month" means the days the employee is required to work under the contract:

• Include public holidays that fall on a normal working day.
• Exclude rest days and non-working days (the Saturday of a 5-day-week employee is a non-working day).

For a Monday–Friday employee, June 2026 has 22 working days; a month with a public holiday on a Tuesday still counts that Tuesday. Because the count moves month to month, the same absence costs a different amount in February than in July — that is the formula working as designed, not an error.

Step 3 — Count the days actually worked

Days worked = working days falling inside the employed (or paid) span. A public holiday inside that span counts as a day worked — it sits in both the numerator and the denominator, so the employee is effectively paid for it. Days of no-pay leave drop out of the numerator only.

Step 4 — Compute, with a worked example

New hire joins Wednesday 17 June 2026 on $4,400 gross a month, Monday–Friday. June 2026 has 22 working days; from 17 June to 30 June there are 10.

$4,400 ÷ 22 × 10 = $2,000 for June.

Same employee takes 3 days of no-pay leave in a 21-working-day month: $4,400 ÷ 21 × 18 = $3,771.43. MOM publishes no rounding rule for this formula — pay to the cent, and if you round, treat it as company practice, not statute.

The daily and hourly rates (different formulas)

For paying work on a rest day, computing encashment, or part-time rates, MOM publishes separate annualised formulas — do not improvise from the incomplete-month one:

Rate	Formula
Daily gross rate	12 × monthly gross ÷ (52 × average working days per week)
Daily basic rate	12 × monthly basic ÷ (52 × average working days per week)
Hourly basic rate	12 × monthly basic ÷ (52 × weekly working hours, typically 44)

The annualised daily rate and the incomplete-month daily rate are deliberately different numbers. The first smooths the year into a constant; the second prices the specific month. Using the annualised rate to pro-rate a joiner's first month is the single most common pro-rata error in DIY payroll.

CPF on a pro-rated month

CPF is computed on the actual wages paid, so a pro-rated month attracts CPF on the pro-rated amount — there is no separate CPF proration step. A $2,000 first-month salary for an employee below 55 attracts CPF on $2,000 at the normal rates; see the CPF guide for the rate bands and the $8,000 Ordinary Wage ceiling.

One timing rule to remember: hire mid-month and CPF is still due for that month, by the 14th of the following month.

Common mistakes to avoid

• Dividing by calendar days (÷30 or ÷31) — the statutory denominator is working days.
• Excluding the public holiday from the working-day count — MOM includes it.
• Using basic instead of gross — allowances under the contract belong in the numerator.
• Annualised daily rate for proration — wrong tool; it exists for rest-day pay and encashment.
• Inventing a rounding convention and calling it statutory — MOM publishes none.

Run the formula once by hand to understand it, then let your payroll software hold the working-day calendars — the denominator changes twelve times a year, and every public holiday shifts it.