Are electronic signatures legally binding?

Yes. Electronic signatures are enforceable in interstate commerce under the ESIGN Act (15 U.S.C. §7001) and under UETA where adopted by the state; ensure intent, consent, attribution, and record retention.

Do invoices require notarization or witness signatures?

Typically no. Standard invoices do not require notarization or witnesses. Use notarization only when a specific transaction or jurisdictional rule explicitly requires it.

What happens if the client provides the wrong tax ID?

If the payer lacks a correct TIN you may be required to apply backup withholding at 24% and the payer may face reporting complications; verify TINs on Forms W-9 ahead of payment.

Can I attach supporting documents?

Yes. Attach relevant deliverable confirmations, receipts, or signed acceptance forms to reduce disputes and create a complete audit trail for accounting and tax purposes.

How should I handle a disputed invoice?

Record the dispute, withhold contested amounts per your contract, negotiate in writing, and preserve all correspondence and evidence in case formal collection or litigation is required.

How long must I keep invoice records?

Retain invoices for at least three years for IRS purposes (IRC §6501(a)); keep longer where industry rules apply, for disputes, or for HIPAA-covered documents per 45 CFR §164.530(j).

Electronic Signature
Templates
Finance
Flat Fee Invoice Template

Flat Fee Invoice Template

This template is fully customizable. Edit the text, fill out the fields, and send it for signature. Give it a try!

FLAT FEE INVOICE

From (Issuer)

Company Name Address Phone Email

Bill To (Client)

Client Name Company / Organization Address Phone / Email

Invoice Number:

Invoice Date:

Due Date:

Payment Terms:

Invoice Details

Description	Quantity	Unit Rate	Amount

Subtotal:

Tax Rate (%):

Tax Amount:

Shipping / Other:

Total Due:

Payment Instructions & Policies

Accepted payment methods: Check (payable to Issuer), ACH / bank transfer, or credit card. Payment must be made in United States dollars unless otherwise agreed in writing. For bank transfer, provide account details below.

Bank / Remittance Instructions

Late payments: Unpaid balances not received by the due date are subject to a late fee of plus interest at % per month (or the maximum permitted by law), calculated monthly on the outstanding balance. Returned checks are subject to a returned check fee.

Terms & Conditions

Issuer certifies that the services or goods described above were provided in accordance with agreed scopes and that the amounts billed represent the full and final fee due for the specified flat-fee engagement, except as otherwise documented in writing. Payment is non-refundable except as expressly set forth in a separate written agreement. Any dispute concerning this invoice must be submitted in writing within ten (10) business days of receipt; failure to dispute timely constitutes acceptance of the invoice as issued.

Collection costs: If collection or legal action becomes necessary to collect amounts due, the client will be responsible for reasonable collection costs, including attorneys’ fees and court costs, to the extent permitted by law. Governing law for this invoice and any disputes arising hereunder is the law selected by the issuer: .

Additional Notes

Issued By:

Signature:

Date:

What the Flat Fee Invoice Template Is

A Flat Fee Invoice Template is a standardized billing form used to request payment for a single, fixed-price service or deliverable. It lists the flat fee, billing date, invoice number, client and vendor contact details, payment terms, and remittance instructions so both parties have a clear, auditable record of the amount due and how to pay. The template is suitable for one-off services or packaged offerings where hourly billing is not used, and it can be saved as a reusable document for consistent billing across clients and projects.

Why Use a Flat Fee Invoice Template

A consistent flat fee invoice reduces billing errors, clarifies expectations for clients, and speeds payment by presenting all necessary payment details in a single, easy-to-review document. It supports accounting, tax reporting, and dispute resolution by producing a uniform record for each sale.

Who Typically Issues a Flat Fee Invoice

Use this template when scope is well-defined, change orders are tracked separately, and both parties agree on a single contract price.

Freelancers and consultants billing a fixed project price for design, writing, or advisory engagements.
Small businesses and agencies issuing packaged services like monthly maintenance or flat-rate installs.
Professional firms (legal, accounting) using fixed-fee arrangements for discrete deliverables.

Step-by-step: Fill Out a Flat Fee Invoice

Follow these steps to create a clear, enforceable invoice that reduces disputes and supports timely payment.

01

Assign Number: Create a unique invoice number for tracking.
02

Set Date: Enter invoice issue date in MM/DD/YYYY format.
03

Describe Fee: State the flat fee and deliverable clearly.
04

Payment Terms: Specify due date, late fees, and accepted payment methods.

Configure an Online Flat Fee Invoice Workflow

Set these fields when preparing a reusable online invoice to automate delivery and tracking.

Field	Configuration
Template Name	Flat Fee Invoice — default for single-price services
Auto-numbering	Enable sequential invoice numbers
Due Date Rule	Net 30 (or custom days) applied automatically
Reminder Schedule	Email reminders at 7 and 3 days before due date

Where to Send or File the Completed Invoice

A clear routing plan reduces confusion: designate the recipient, delivery channel, and any internal filing steps.

Client Accounts Payable: Send to the payer's AP email or portal address.
Accounting System: Upload to your accounting or ERP system for reconciliation.
Client Records: Provide a copy to the client contact for their records.
Internal Archive: Store the signed invoice in a secure document repository.

Delivery and eSubmission Options

When using digital delivery, confirm the recipient can receive your file format and retain a copy that includes an audit trail for payments and disputes.

Email: Attach PDF invoice
Portal Upload: Post to client portal
eSignature: Use lawful e-signature

Key Dates and Timeframes to Note

Track these standard deadlines to manage cash flow and reporting obligations related to invoicing.

Issue Date:

Date invoice is created and sent to client.

Due Date:

When payment is contractually required (e.g., Net 30).

Late-Fee Trigger:

Date after which late fees may be applied per terms.

Dispute Window:

Client should report billing disputes within a defined period.

Tax Reporting:

Keep invoice for tax reporting; 1099-NEC deadlines may apply for contractors.

Common Mistakes When Preparing a Flat Fee Invoice

Using vague descriptions that create scope disputes and delay payment resolution.
Entering incorrect client names or tax IDs, leading to bookkeeping and 1099 mismatches.
Failing to specify payment terms, which removes leverage for prompt payment enforcement.
Not attaching proof of delivery or completion, increasing the risk of unpaid invoices.

Penalties and Risks of Incorrect Invoices

Late Payment: Cashflow harm

Incorrect TIN: Backup withholding

Missing Terms: Collection difficulty

Disputed Scope: Delayed settlement

Tax Reporting: IRS penalties

Data Exposure: Privacy risk

Essential Elements of a Professional Flat Fee Invoice

A complete invoice combines legal, financial, and practical details so it is actionable, auditable, and suitable for accounting and tax records.

Invoice Number

A unique identifier used for tracking, payment matching, and recordkeeping; include a consistent prefix or format to avoid duplicates across clients.

Contact Details

Full vendor and client names, addresses, and billing contacts so remittance and dispute questions are routed correctly and quickly.

Service Description

One-line description of the flat-fee deliverable plus any invoice-specific scope limits to reduce ambiguity in billing disputes.

Flat Fee Amount

The exact amount due in USD, clearly showing subtotal, taxes (if applicable), and the total due to eliminate calculation errors.

Payment Terms

Due date, accepted payment methods, late fee policy, and early-payment discounts where applicable to set clear expectations.

Remittance Instructions

Bank account, ACH routing, wire instructions, or online payment link to streamline payment and reduce processing delays.

How to Save and Share the Completed Invoice

Choose formats that preserve layout, support signatures, and integrate with accounting systems.

PDF (Recommended)

Export a PDF to preserve formatting and include an embedded audit trail when using a compliant eSignature platform for legally traceable acceptance.

DOCX Template

Keep an editable DOCX master for quick updates; convert to PDF before sending to avoid accidental edits after issuance.

CSV for Accounting

Export key invoice data (number, date, amount, client) as CSV to import into bookkeeping or ERP systems.

Signed Copy Archive

Store signed PDFs or copies with proof of delivery in a secure repository for audit and tax records.

eSignature Pricing Comparison (signNow First)

Compare common vendor pricing and basic capabilities for eSignature use with invoices. Plan details and features vary by vendor and tier.

	signNow	DocuSign	Adobe Sign	PandaDoc	HelloSign
Starting Price	$8/user/mo	$15/user/mo	$14/user/mo	$19/user/mo	$15/user/mo
Free Trial	7-day free trial	Varies	Varies	Varies	Varies
Bulk Send	Yes	Yes	Yes	Yes	No
Audit Trail	Yes	Yes	Yes	Yes	Yes
HIPAA Compliant	Yes	Yes	Yes	No	No
Envelope Cap	No cap	100 envelopes/user/year	Varies	Varies	Varies

Frequently Asked Questions About Flat Fee Invoices

Answers to common legal, technical, and processing questions when using flat fee invoice templates.

Need help? Contact support

Are electronic signatures legally binding?
Yes. Electronic signatures are enforceable in interstate commerce under the ESIGN Act (15 U.S.C. §7001) and under UETA where adopted by the state; ensure intent, consent, attribution, and record retention.
Do invoices require notarization or witness signatures?
Typically no. Standard invoices do not require notarization or witnesses. Use notarization only when a specific transaction or jurisdictional rule explicitly requires it.
What happens if the client provides the wrong tax ID?
If the payer lacks a correct TIN you may be required to apply backup withholding at 24% and the payer may face reporting complications; verify TINs on Forms W-9 ahead of payment.
Can I attach supporting documents?
Yes. Attach relevant deliverable confirmations, receipts, or signed acceptance forms to reduce disputes and create a complete audit trail for accounting and tax purposes.
How should I handle a disputed invoice?
Record the dispute, withhold contested amounts per your contract, negotiate in writing, and preserve all correspondence and evidence in case formal collection or litigation is required.
How long must I keep invoice records?
Retain invoices for at least three years for IRS purposes (IRC §6501(a)); keep longer where industry rules apply, for disputes, or for HIPAA-covered documents per 45 CFR §164.530(j).

be ready to get more

Join over 28 million airSlate SignNow users

Sign Now