Procedures in accomplishing the BIR Form No. 1600WP
Steps
 Hint: Use tab to move to the next enterable field
1
 Indicate the period for Item 1 by supplying the From date in MM/DD/YYYY format. 
2
 Number of attachment in Item 3 will automatically increment as you attach a file.
3
 Indicate the category of withholding agent in Item 7.
4
 Indicate if there are any taxes withheld in Item 4. Selecting Yes will enable fields under Part II - Computation of Tax and Schedule 1.1.
5
 Item 11 is defaulted to No. The said field is disabled.
6

Supply applicable tax base under Tax Base column of Part II computation of tax after selection of ATC by clicking the hyperlink. Tax Required to be Withheld will be automatically computed based on
the rate specified on the form. 
7
 Fill up Schedule 1.1 and supply necessary fields as needed. ATC can be
supplied by clicking on the hyperlink and selecting from the list. Complete all data for each row by filling the Payee details and value of Amount. Tax Required to be withheld column will automatically compute after completion of required columns.
8
 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.
9
 Grayed out fields will be automatically computed upon either completing required fields or clicking on validate button.
10
 Press or Click the Validate Button.
11
 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 11.
12
 Review the data you have just encoded then click on verify to have an automated validation process. The taxpayer will be prompted if any problems were encountered. Otherwise, a successful validation will enable the Submit button. 
13
 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.
14
 A reference number will be given by the system for filed tax return.