The form model

SPF automates the tax paperwork employers collect during onboarding: the federal W-4, Alabama’s A-4, Ontario’s TD1ON, and hundreds of others. In everyday use, “a form” means that piece of paper. In SPF, a form is the paper’s digital equivalent: the questions that need answering, the logic for which questions apply, and the metadata that ties it all back to the official document. That’s the form model this page covers. It’s separate from determination, the step that decides which forms an employee needs in the first place, covered in Form determination. Once a form is determined, its own model (described below) governs how it gets filled out and returned.

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How a form identifies itself

Wherever SPF returns a form (in form determination, in guided flows, in the catalog, in the completed-form response), it carries the same identifying fields. Show employees formName and formTitle. Use formId everywhere in your code; it’s the value that stays stable across revisions.

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Form IDs follow a pattern

Form IDs aren’t arbitrary. Once you know the pattern, you can usually read one at a glance. U.S. state and local forms combine the two-letter state abbreviation with a three-digit number. The 101 slot is generally the state’s primary resident withholding form, and higher numbers are the state’s other forms: nonresident certificates, exemption claims, military spouse forms, and local jurisdiction forms.

• AL101: Alabama’s primary withholding form
• NY102: a New York nonresident allocation certificate
• MI110 through MI132: Michigan’s city income tax forms
• PA114: Pennsylvania’s local earned income tax residency certification

U.S. federal forms use a W prefix:

• W4101: Form W-4, Employee’s Withholding Certificate
• W6101: Form 673, for claiming exemption on foreign earned income
• W8101: Form 8233, for nonresident aliens claiming a treaty exemption

Canadian forms are built from the TD1 family, with the province or territory appended:

• TD1: the federal Personal Tax Credits Return
• TD1ON, TD1AB, TD1BC: Ontario, Alberta, British Columbia
• TP1015, TP1016, T1213: Quebec source deductions and related federal forms

Officially translated forms carry a language suffix: SP for Spanish in the U.S., FR for French in Canada. W4101SP is the IRS’s own Spanish W-4; TD1ONFR is the CRA’s French Ontario TD1. These are separate form IDs, not a display setting. See Languages and locales for when to use them.

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Form types

Every form carries a formType describing its purpose. This is what lets you group forms sensibly in your interface, decide which ones need employer follow-up, and understand why an employee received a particular set. These are the ones you’ll see most often:

• Resident: the standard withholding certificate for someone who lives in the jurisdiction
• Nonresident: for someone who works in the jurisdiction but lives elsewhere, often under a reciprocal agreement
• Local: a city, county, or municipal withholding form
• Exempt: a claim for exemption from withholding
• Canada Resident: federal and provincial Canadian withholding forms

The remainder are narrower, and several are specific to one jurisdiction or population: Resident working outside state, military, Earned income credit, Pension, Exempt-student, Exempt Native American, Nonresident employer, Resident allowance adjustment, Nonresident Fort Campbell, Exempt tax credit, Resident Pittsburgh, Nonresident Pittsburgh, Tax adjustment, and Exempt military spouse. To identify local forms programmatically, formType reports Local in the API, and Hosted postback clients get "isLocalForm": true in the transaction log. See Local withholding forms for the full list of local forms SPF supports.

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Variants of the same form

Some forms exist in more than one version at the same time, for reasons other than an annual revision:

• Language variants: the officially published Spanish or French edition of a form, such as CA101 and CA101SP
• Jurisdiction variants: several states build their withholding form directly on the federal W-4. Colorado (CO101), North Dakota (ND104), New Mexico (NM101), and Utah (UT101) all use the W-4 document itself, which is why passing an employee’s existing federal elections into those forms shortens the interview considerably

Variants are independent form IDs. Determine which one the employee needs, then work with that ID consistently for the rest of the session.

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Browsing everything SPF supports

You have three ways to see the full set of forms, depending on what you need.

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