fyllyoLast year’s worksheet
Payroll files keep earlier worksheets next to the current one. Software can copy an old result.
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Fill Form W-4 with AIEmployee's Withholding Certificate
Add the employee’s withholding election, any worksheet and the employment record. Fyllyo fills Form W-4 on your Mac and shows the lines behind each answer for you to check.
Where AI form filling goes wrong on Form W-4
Form W-4 tells an employer how much income tax to hold back from each paycheck. It is short, but the file behind it can hold several concurrent jobs paid weekly, biweekly or monthly, last year’s Multiple Jobs Worksheet, a former address and an employer record full of other numbers. Annual wages and per-paycheck amounts sit side by side. These are the common places AI tools and autofill get it wrong. What the form requires is for the IRS to say. Follow its instructions. IRS official page for Form W-4.
Extra withholding from two places
The amount per pay period can come from a worksheet plus an extra amount the employee asks for in another document. Software can take one and miss the other.
Three jobs and a checkbox
With several jobs in the file, software can tick every option Step 2 offers at once.
The Employers Only box
The bottom of Form W-4 is for the employer, and an onboarding record lists a workers’ compensation policy number, a carrier and a pay schedule near the EIN. Software can put any of them in the EIN box.
Where the employee lives now
A withholding election often notes where the employee lived before moving. Software can copy that street into Step 1.
How Fyllyo takes care of them
With a test client and four documents (a Social Security card copy, the employee’s withholding election, a Multiple Jobs Worksheet and the employment record), Fyllyo filled 14 fields in 20 seconds. It left the Social Security number for the employee, because the card copy shows it masked.
- Last year’s worksheet. Reads the current worksheet. In the test, line 2c was 9,900, not the 9,100 from the 2025 worksheet in the file.
- Extra withholding from two places. Adds them up. In the test, 380.77 from the worksheet and 19.23 requested gave 400.
- Three jobs and a checkbox. Follows the employee’s election. In the test, the worksheet lines were filled from the worksheet and the two-jobs box stayed empty.
- The Employers Only box. Puts the transit company’s EIN, its address and the first day of work in the employer’s box. In the test, the workers’ compensation policy number never reached the form.
- Where the employee lives now. Step 1 gets the home the election lists as the residence today: 906 Copper Street in the test, while the Alder Crescent home the employee left in 2025 was ignored.
How much of a Form W-4 does Fyllyo fill?
Fyllyo can fill all 48 fields on Form W-4 from the client’s documents. Lines the documents don’t support stay blank and are listed for you to check.
You confirm on every form
- Employee's first name and middle initial
- Employee's last name
- Employee's social security number
- Extra withholding per pay period
- Total income
- and 1 more
What do you give Fyllyo?
Fyllyo reads the documents you already have. These can be PDFs, scans, photos, Word files or typed notes, and you can add several at once. Fyllyo works out which document answers which line.
Client data stays on your Mac
Client documents and the filled form never leave your computer. Fyllyo uploads nothing. Once it is set up, filling works offline.
What Fyllyo doesn’t do
Fyllyo doesn’t decide what to file, give legal or tax advice, or submit Form W-4 for you. Use the IRS’s official page for Form W-4 and your professional judgement. Fyllyo does the reading and the typing.
What if a document is a scan or a photo?
Fyllyo reads scans and photos as well as PDFs, Word files and typed notes. Clear, readable copies give the best results, and every answer on Form W-4 still shows the line it came from.
Fill your next Form W-4 on your Mac
Try form filling free for 5 days. Then buy Fyllyo Paid once for $99. It is a lifetime licence with free updates and no subscription. Filling forms on your Mac uses no AI credits. Pricing and licence details.