What deposit percentage is standard for window installation projects?

In the window and fenestration industry, 30-50% upfront deposit is the norm. For projects above £10,000 / €10,000, a three-stage structure is common: 30% at approval, 40% at material delivery, 30% on completion. For residential customers, paying that deposit by iDEAL or bank transfer is the most common arrangement.

What payment terms can I legally include in my quotes?

You can include statutory interest for late payment (8%+ per year for B2B under the Late Payment of Commercial Debts Act in the UK, or EU Directive 2011/7/EU), recovery costs, and a right of suspension if payment is not received. For B2C customers, different rules apply — always check the regulations in your country.

When should I send the final invoice?

Send the final invoice at handover, not after. Get a handover sign-off from the customer — digitally or physically — at the moment of completion. This establishes the payment obligation and prevents disputes about 'it's not finished yet'.

How do I handle a customer who won't pay?

Step 1: friendly automatic reminder on the due date. Step 2: formal notice with statutory interest after 14 days. Step 3: debt collection agency or legal action. For B2B: you can exercise your right of suspension — suspend further work for the same client until the outstanding invoice is paid.

Can I require full upfront payment from new customers?

Yes, there is no legal maximum on deposits. In practice, 50% upfront for new business customers is the market standard; more than that can raise suspicion. For residential customers, 100% upfront is unusual — 30-50% is the typical expectation.

Payment terms for window installation quotes — deposits, milestones and late payment

Cash flow is the oxygen of every window installation business. You pay for materials at order, labour runs continuously, and customers pay at — or after — completion. Without solid payment terms, you are financing your customer. Below: a practical framework for deposits, milestone invoicing and late payment — with template language you can drop into your quotes today.

Why payment terms belong on the quote — not just the invoice

Many installation businesses only state payment terms on the invoice. That is too late: when the customer signs the quote, the commercial terms are already agreed. If the customer approves a quote without seeing the payment schedule, they are less legally bound to payment conditions introduced only on the invoice later.

Practical rule: put payment terms in a visible section on page one of the quote — not buried in the terms and conditions appendix.

Deposit structure — how much and when?

The deposit serves two functions: cash flow (you cover your material costs before ordering) and commitment (a customer who has paid rarely cancels). Market standard in the fenestration industry in 2026:

Project value	Deposit at approval	Interim payment	Balance on completion
Under £/€5,000	50%	—	50%
£/€5,000 – £/€15,000	40%	30% at material delivery	30%
£/€15,000+	30%	40% at delivery + installation start	30%

Tying the deposit to the approval is the most efficient method. The customer signs digitally in the quote portal and, as soon as the instalment falls due, sees there exactly what to transfer: the amount, your IBAN and a unique reference. No separate payment request to write days later, and no argument afterwards about which figure was agreed.

Milestone invoicing — when and how

For larger projects (window replacement across a multi-unit block, new-build contract), milestone invoicing works best. Tie payment triggers to verifiable, objective events — not calendar dates that can slip:

Milestone 1 — approval: 30-40% deposit. Customer confirms the job, you order the windows.
Milestone 2 — material delivery: 30-40% invoice. Windows are delivered to site or depot. Customer can inspect.
Milestone 3 — handover: remaining 20-30%. Send immediately after the handover sign-off, while the customer is still on site and satisfied.

Always tie milestones to verifiable events — "upon delivery of materials to site" is clearer than "week 32." Calendar-based milestones create disputes when timelines shift.

Template payment terms for your quote

Add this as a separate, visible section in the quote before the signature block:

Payment terms

A deposit of [X]% (£/€[amount] excl. VAT) is due within 5 working days of signing this quote, payable by bank transfer using quote reference [reference]. The balance of [Y]% is invoiced upon completion and due within 14 days of invoice date. Late payment will incur statutory interest at the applicable rate under [Late Payment of Commercial Debts Act 1998 / EU Directive 2011/7/EU], plus reasonable recovery costs.

Template invoice payment reminder language

Please pay the outstanding amount of £/€[total] within 14 days of this invoice date by bank transfer to [account details], quoting invoice number [number]. If payment is not received by the due date, statutory interest will be applied at the rate applicable under [Late Payment Act / applicable law], together with reasonable debt recovery costs.

B2B vs B2C — key legal differences

B2C (residential customers) — statutory cooling-off period of 14 days applies for contracts concluded off-premises (at the customer's home). Make sure customers are informed of this right in the quote. Late payment interest rates and recovery costs are regulated and typically lower than B2B.
B2B (contractors, developers, housing associations) — statutory interest for late payment is significantly higher (UK: 8% over base rate; EU: 8% + ECB rate). Maximum payment terms of 60 days under EU Directive unless explicitly agreed otherwise. You can and should agree shorter terms — 14 or 30 days is common.

Handling late payment — step by step

Day 1 after due date: automated friendly reminder by email. A large percentage of late payments are simply forgotten — a non-accusatory reminder resolves most cases.
Day 14: formal notice specifying the statutory interest accruing, with a final 7-day deadline.
Day 21: escalate to a debt collection agency or legal representation, or call the customer directly if the relationship allows it.
B2B — right of suspension: if you are doing ongoing work for the same client, you can legally suspend further work until the outstanding invoice is settled. This is one of the most powerful tools available. State this right in your general terms.

How Kozynofferte records payment terms

In Kozynofferte you set your standard payment schedule once: the percentage you ask at order, what follows after production and what is left after handover. At quote approval via the customer portal the deposit is fixed as an agreement; as soon as that instalment falls due the portal shows the customer the amount, your IBAN and a unique reference, and they transfer it straight to your account — no payment provider in between, so no transaction fee on your revenue. You tick the payment off when it lands; the invoice and the confirmation email then go out automatically. Every stage in your schedule (deposit, milestone, balance) gets its own invoice that way.

Try free for 14 days — no credit card required. Or see how the portal works.

Specific payment situation or legal question? Email me directly — this is general information, not legal advice.

— Richard Bajnath, founder of Kozynofferte