Articles | Updated 21 October 2026
How to file the P.N.D.1 online from your payroll software
A business with employees must withhold income tax from their salaries (if they reach the threshold), file the P.N.D.1 every month, and summarize the whole year with the P.N.D.1A by February of the following year. Filing online requires a file in the format set by the Revenue Department, which good payroll software should be able to create from the payroll runs you have already calculated.
How is the P.N.D.1 different from the P.N.D.1A?
The P.N.D.1 is a monthly form covering only employees who had tax withheld that month. Since 2567 it must be filed electronically, by the 15th of the following month. The P.N.D.1A is an annual summary that must list "every" employee who received a salary that year, even those with no tax withheld at all. It is due by the end of February.
Employees whose salary is below the taxable threshold do not appear on the monthly P.N.D.1 but must appear on the P.N.D.1A. Small businesses often get this wrong.
Calculating withholding tax on salaries
The standard method is to estimate the full year's income (salary × 12 plus other income known in advance), subtract the expenses and allowances the employee has declared (form L.Y.01), calculate the full year's tax at progressive rates, then divide by the number of pay periods. If allowances change during the year, you recalculate from that period onward.
Besides tax, you also need to deduct the employee's social security (SSO) contribution at the rate and wage ceiling announced by the Social Security Office, and remit it together with the employer's share by the 15th of the following month.
Creating the file for filing through RD Prep
The Revenue Department's e-Filing system accepts text files in a set format (column order, field lengths, and Thai character encoding in TIS-620). Files typed by hand often get the character encoding or date format wrong, and the system rejects them.
In GORINY, once a payroll run is approved, the P.N.D.1 and P.N.D.1A report pages include employees according to the rules above and create a text file for import into the Revenue Department's RD Prep program. The data used is the national ID number, income and tax actually withheld in closed payroll runs, so it matches the payslips your employees received.
Checklist before closing a payroll run
- Every employee has a national ID / taxpayer ID number on record
- Allowances (L.Y.01) are updated for this year
- Working days, overtime and unpaid leave are correct before calculating
- Employees who joined or left mid-month are calculated by actual days worked
- Approve the run before creating the filing file. The file must come from closed figures, not a draft
Frequently asked questions
- I have 2 employees whose salaries are below the taxable threshold. Do I need to file?
- You do not need to file the monthly P.N.D.1 if there is no tax to withhold, but you must file the annual P.N.D.1A and list every employee.
- What do I need to sign up for before filing online?
- You need a Revenue Department e-Filing user account in the business's name (a one-time sign-up). After that, import the file the app creates into RD Prep and file through e-Filing every month.
- Does GORINY calculate social security too?
- Yes, in the same payroll run, for both the employee and employer shares, using the rates and ceiling configured in the system.
Sources
Checked against official announcements on 21 October 2026
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