Sage Integration for Construction Payment Applications

If you run your construction payments in one place and your accounts in Sage, you know the problem: every approved application gets keyed in twice. Once to value the work, again to raise the invoice. Double entry wastes time and quietly introduces errors, and on a busy month it is the first thing to slip.

The Sage integration in BuildQS removes that second keying. You build and approve a payment application as normal, then export it to Sage Business Cloud Accounting as a sales invoice in a couple of clicks, with retention, deposits and VAT treatment already worked out.

This guide explains what the Sage integration does, how the workflow runs end to end, what it handles automatically, and the one thing you need to set up in Sage first.

What the Sage integration does

The Sage integration connects your BuildQS account to Sage Business Cloud Accounting so an approved payment application can become a Sage sales invoice without re-typing the figures. BuildQS stays the place you value work and track retention; Sage stays your accounting system. The integration is the bridge between the two.

In practice it means:

• One source of truth for the numbers, your approved application.
• No manual re-entry of line items, retention or deposits into Sage.
• A clear link between the BuildQS application and the Sage invoice it created.

A quick note on scope: a BuildQS business connects either Sage or Xero, not both at once. You pick the accounting system you actually use and connect that one.

See the Sage workflow in action

Before the step-by-step guide, watch the full workflow from an approved application to a finished sales invoice in Sage.

The walkthrough below shows the export running from start to finish, including how retention and the invoice link appear once it is done.

How the workflow runs, step by step

The export is a deliberate, explicit step. BuildQS does not silently push every application to Sage the moment it is submitted, because you usually want the figure agreed first. Here is the order.

1. Build and approve the application. Value the work, add any variations, and get the application to approved as you normally would.
2. Open the invoice. From the approved application, open the invoice in BuildQS where you choose how it should appear.
3. Choose the line-item detail. Export as a single summary line, one line per phase, or a line per task, depending on how much detail your client and your accounts need.
4. Export to Sage. BuildQS creates the matching sales invoice in Sage with the values, retention and any deposit already in place.
5. Review in Sage. The invoice lands in Sage ready for you to check and send. Nothing is hidden; you keep full control on the accounting side.

Because the link between the application and the Sage invoice is stored, you can always see which application produced which invoice, rather than hunting through Sage to match things up later.

What it handles automatically

The point of the integration is that the awkward construction-specific lines are dealt with for you.

• Retention. The amount held back is reflected on the export rather than left for you to calculate and add by hand.
• Deposits and advance payments. Where an advance has been deducted on the application, that deduction carries through.
• Analysis types. Sage analysis types, the Sage equivalent of tracking categories, can be attached so the invoice lands against the right part of your accounts.
• Line-item modes. Summary, per phase, or per task, so the invoice matches how you present valuations.
• VAT, including reverse charge. Standard and reduced rates are handled, and the domestic reverse charge is supported (see the setup note below).

VAT reverse charge: the one thing to set up first

The domestic reverse charge (DRC) for construction works through the Sage integration, but it depends on one piece of setup that has to be done inside Sage, not BuildQS.

For Sage to accept a reverse-charge invoice, the customer in Sage must be set up with:

• their CIS registration ticked on the contact, and
• a VAT number recorded against them.

This is a Sage requirement, not a BuildQS limitation. Sage's API will not let any connected app set those fields for you, so it is a one-time job on each reverse-charge customer in Sage. Once that customer is configured, BuildQS sends the invoice with reverse charge applied and Sage records the notional VAT correctly. If the customer is not set up, the export will tell you what is missing rather than failing quietly.

If you are new to the reverse charge itself, the rules on who it applies to and how it is shown are worth getting right before you export anything. It changes which party accounts for the VAT, so an invoice raised the wrong way causes problems downstream.

How invoice status stays up to date

When you mark an invoice as paid or void it in Sage, BuildQS reflects that the next time you open that application. The status is checked against Sage when you view the application, so an invoice you settle in Sage shows as paid in BuildQS without you updating it twice.

It is worth being clear about what this does and does not do. The check happens when you open an application, so the picture is accurate where it matters most, on the screen you are actually looking at. It is not a live background feed across every project at once. If you have settled several invoices in Sage and want everything refreshed, open the applications or use the manual sync.

Keeping invoice status straight is part of avoiding the cash-flow blind spots that come from not knowing what has actually been paid. For your rights and options when an invoice runs past its due date, see our guide to late payments in construction.

How this fits the bigger picture

Exporting cleanly to Sage is one piece of running a tighter commercial operation. The same approved figures that feed your Sage invoice also feed whether the job is actually making money. If you want to pressure-test that, our guide to construction profit margins walks through what you really keep once retention, variations and overheads are accounted for.

Prefer to walk through your workflow live first? Book a Demo

Frequently asked questions

Can I connect both Sage and Xero to BuildQS?

No. A BuildQS business connects to one accounting system at a time, either Sage or Xero. You connect whichever you actually use for your accounts. This keeps a single, unambiguous path from an approved application to one invoice in one system.

Does BuildQS send invoices to Sage automatically?

No, and that is deliberate. Exporting to Sage is an explicit step you take from the approved application, because the value is usually agreed first. You stay in control of when an invoice is created and you review it in Sage before sending.

Does the Sage integration handle the CIS tax deduction?

No. The integration handles VAT, including the domestic reverse charge, but it does not apply the CIS income-tax deduction (the 20% or 30% withholding on labour). That is a separate calculation. The reverse charge and the CIS deduction are often confused, but they are different things.

Why does my reverse-charge export get rejected?

Almost always because the customer is not set up for reverse charge in Sage. Sage needs that customer to have CIS registration ticked and a VAT number recorded. Add both on the contact in Sage, then export again. BuildQS cannot set those fields for you because Sage's API does not allow it.

Sources

• Sage, Sage Business Cloud Accounting product and developer documentation, on sales invoices and VAT handling (sage.com).
• HM Revenue & Customs, VAT domestic reverse charge for building and construction services guidance (gov.uk).

This guide is general information for UK subcontractors, not tax or accounting advice. VAT reverse charge treatment should follow current HMRC rules and your own contract terms. Reviewed, last reviewed 8 June 2026.