Procedures in accomplishing the BIR Form No. 1601F
Steps
 Hint: Use tab to move to the next enterable field
1
 Indicate the month and year in item 1. This field is pre-populated or defaulted to prior month of the current year.
2
 Item 2 is predetermined by the system depending on the supplied month & year in item 1.
3
 Item 3 is predetermined by the system depending on the no. of sheets attached.
4
 Indicate if there are any taxes withheld in item 4. Selecting No will disable fields under Computation of Tax. This is a mandatory field.
5
 Indicate category of withholding agent in item 12. This is a mandatory field.
6

Change the default value under Item 13 if you are availing of Tax Relief. If Yes is specified, the "If yes please specify" drop down box will become mandatory.
7
 Supply values in the Tax Base column where applicable. The Tax Required To Be Withheld, Total Tax Required To Be Withheld and Remitted Based on Regular Rates, Total and Tax Still Due/(Overremittance) are automatically computed by the system upon validation. 
8
 Item 15 is mandatory if you have chosen "Yes" in item 13. Click  Schedule 1 link and select Treaty Code & ATC from the list provided.  The Nature of Income Payment & Rate column is auto populated depending on the ATC you have chosen. The Rate column will remain editable since it varies for different countries and can be changed as necessary. Supply value in Amount of Income Payment for the computation of Tax Required to be Withheld. 
9
 Item 17 is enabled if you are filing an amendment. This field will retrieve value from the database if a payment has been made in the original return, else a zero value is displayed. This field will remain editable. Change the values as necessary to supply correct info. 
10
 Grayed out fields will be automatically computed after required fields are filled up or after clicking the validate button.
11
 Penalties, Item 19A, 19B, 19C will be automatically computed by the system upon validation.
12
 The taxpayer can now attach supplementary documents by clicking on the Add Attachment button. A separate window will be displayed to facilitate the process. Attachments are done on a per file basis.  

Please note that the system currently accept files of the following format
only: *.zip, *.xls, *.dat, *.csv. The taxpayer will be prompted if the file is not a valid format.

We do suggest that you upload your files in zip format to shorten the process.
13
 Press or Click the Validate Button.
14
 The system will prompt you if there is any problem with the supplied information, and correct this accordingly. After the necessary correction, you may again validate the return form by repeating Step 13. 
15
 If the form was successfully validated by the system, you may review or check the outcome of the validation by observing the following computed fields in item nos.: 14, 16, 18, 19D, 20
16
 If you want to edit some input fields you may do this by clicking the Edit Button located on the bottom of the page. Or, if you are already satisfied with the result and all the information is correct you may already submit this by clicking the Submit Button beside the Edit Button.
17
 A reference number will be given by the system for filed tax return.