Advance Invoices in Tranches: How to Bill Large Projects Cleanly

For a large web project, an interior renovation, or a multi-month consulting mandate, a single advance invoice often isn't enough. Instead, you agree with the client on three, four, or five payment milestones – and this is exactly where most mistakes happen in practice: incorrect numbering, missing cross-references between documents, and at the end a final invoice that simply doesn't add up.

Why multiple tranches make sense

For projects with a total volume of around CHF 20,000 or more, a single upfront payment of 30–50% is financially difficult for many clients. At the same time, you as the service provider don't want to advance funds out of pocket. The solution: staggered deposits tied to project progress or calendar milestones.

Typical scenarios:

• Construction: deposit upon contract signature, then upon foundation, interior completion, and final handover
• IT and software projects: deposit at kick-off, then after each sprint or release
• Consulting mandates: monthly advance payments over the duration, final invoice after project completion
• Event planning: deposit upon booking, further tranche 30 days before event, balance after execution

The structure depends on your cash flow and project risk. The real challenge isn't deciding how much to ask upfront – it's managing the follow-up documents cleanly.

Numbering and document structure

As soon as you issue more than one advance invoice for the same project, you need a consistent logic. This schema has proven effective:

Document	Example number	Purpose
1st advance invoice	2026-047-AK1	Deposit tranche 1
2nd advance invoice	2026-047-AK2	Deposit tranche 2
3rd advance invoice	2026-047-AK3	Deposit tranche 3
Final invoice	2026-047-SR	Remaining balance after deducting all advances

The project number (here: 047) is the connecting link. Without it, you and your client quickly lose track – especially if you're managing many projects in parallel.

Alternatively, some businesses number sequentially (2026-047, 2026-048, 2026-049 …) and simply write in the subject line "Advance invoice 1 of 3 – Project Sample Order". This is also permissible as long as the reference is clear.

Mandatory fields on every single advance invoice

Each tranche is a standalone document. This means: complete invoice mandatory fields on every page – no shortcuts because "the client already knows it".

Specifically, every advance invoice must include:

• Your full company name, address, and UID number (VAT number)
• Invoice date and unique invoice number
• Description of services with reference to the overall project ("Advance payment tranche 2 per quote no. …")
• VAT amount and tax rate (normally 8.1%; for certain sectors 2.6% or 3.8%)
• Payment terms and QR-IBAN for QR-bills
• Note on the advance nature ("Amount will be credited on the final invoice")

The last point is crucial: if the note is missing, confusion can arise – or your client might mistakenly record the payment as a final payment.

VAT on staggered advances handled correctly

Under the accrual method: issue VAT on every advance invoice. Tax liability arises at the time of invoice issuance (accrual basis) or upon payment receipt (cash basis). Both methods work for tranches – consistency is what matters. Don't switch methods within the same project.

On the final invoice, deduct all net advances already received and calculate VAT only on the remaining balance. Under no circumstances should you show VAT on the total amount and then deduct the gross advance – that results in excessive tax liability.

Example with three tranches (total contract CHF 30,000 excl. VAT):

• AK1: CHF 8,000 + 8.1% VAT = CHF 8,648
• AK2: CHF 8,000 + 8.1% VAT = CHF 8,648
• AK3: CHF 8,000 + 8.1% VAT = CHF 8,648
• Final invoice: CHF 6,000 (net remainder) + CHF 486 VAT = CHF 6,486
• Total VAT paid: CHF 2,430 – exactly 8.1% on CHF 30,000

This logic also works if the total price changes due to additional items. In that case, list any supplements separately on the final invoice before deducting the total advance.

Common mistakes with multiple advances

Mistake 1: Advance amounts are added up but not individually documented. Consequence: The accountant or auditor can't verify the client's input tax deductions because no separate invoices exist. Each tranche needs its own document.

Mistake 2: Missing overview of all advances on the final invoice. The final invoice should list all previous advances by name – with date and invoice number. A simple block is sufficient:

Less advances already paid:
  AK1 (2026-047-AK1, 15.01.2026)   – CHF 8,000.00
  AK2 (2026-047-AK2, 01.03.2026)   – CHF 8,000.00
  AK3 (2026-047-AK3, 15.04.2026)   – CHF 8,000.00
Net remaining balance:               CHF 6,000.00

Mistake 3: Payment receipts not monitored. If you issue a tranche before the previous one is paid, you risk having multiple open items. Decide internally whether you trigger tranches by schedule or by payment.

Mistake 4: Same QR reference number on every invoice. Each invoice needs its own QR reference so payments can be automatically matched. With the SnapBill app, the reference number is uniquely assigned per invoice – preventing mix-ups in your client's online banking.

Documentation and filing

Create a folder per project (physical or digital) containing:

• Quote or contract
• All advance invoices in chronological order
• Payment confirmations / bank statement excerpts
• Final invoice

This isn't optional – it's mandatory: in Switzerland, documents must be kept for at least 10 years. In a tax audit or VAT inspection, you must be able to demonstrate the entire payment flow without gaps.

If a tranche is ever recorded incorrectly or an invoice needs later adjustment, the guide on canceling or correcting advance invoices explains how to proceed correctly.

At a glance

• Assign a consistent project number and number advance tranches sequentially (AK1, AK2, AK3 …).
• Each advance invoice is a complete, standalone document with all mandatory fields.
• Show VAT on each tranche; on the final invoice only on the remaining balance.
• List all previous advances on the final invoice in table form.
• Each invoice gets its own QR reference number.
• Verify payment of the current tranche before issuing the next one.
• File all documents by project and retain them for 10 years.

With this structure, your billing runs smoothly – whether you issue three or ten tranches – in an auditable, transparent way for your client. SnapBill helps you create professional invoices without resetting the basic structure every time.