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Why is my installment invoice locked?

Do you work with instalment invoices? Then it can happen that you can no longer change or delete an advance invoice or progress claim invoice you drew up earlier. This is not an error: as soon as an instalment invoice is included in the overview of instalment invoices on a subsequent (cumulative) invoice or progress claim, Robaws locks that instalment invoice automatically.

Why is an instalment invoice locked?

With a cumulative invoice strategy, Robaws automatically deducts the amount of the previous instalment invoices from the total on the next invoice (or progress claim). If you could still change the amount of such an instalment invoice afterwards, the deducted amount would no longer match the actual instalment invoice — resulting in an incorrect invoice amount.

To avoid that, Robaws locks an instalment invoice as soon as it appears in the overview of instalment invoices of another invoice or progress claim. That way the total amount always stays correct.

Example: you draw up a quotation with an advance invoice, and afterwards you invoice the rest (for example the execution) via a cumulative invoice. That next invoice shows an overview of instalment invoices containing your advance invoice, and takes it into account automatically:

Overview of instalment invoices on the next invoice: the advance invoice is included and is settled automatically.

If you could still change the amount of that advance invoice afterwards, this overview would not update automatically and the settled amount would no longer match the actual advance invoice — resulting in an incorrect invoice amount. Thanks to the lock, this can no longer happen.

What do you see when an instalment invoice is locked?

If you open the instalment invoice, you see "Locked" at the top. Click "Show info" to see the reason: for example "This invoice is used as an advance invoice on: [name of the other invoice]", with a link to that invoice. You can then no longer change the data.

A locked advance invoice: "Locked" appears at the top with a link to "Show info", which shows the reason.

This is a specific lock for instalment invoices, separate from the general 'Lock' function for quotations, invoices, work orders, and so on. You therefore do not undo this lock with the 'Undo' button.

Do you still want to change something on a locked instalment invoice?

First remove the instalment invoice from the overview of instalment invoices on the linked invoice or progress claim. As soon as it is no longer in that overview, it is no longer locked and you can change it again. Afterwards you add it back, with the correct amount, via the + sign in the overview.

Do not forget to check the total amount of the linked invoice or progress claim after making your changes.

Frequently asked questions

Does this apply to all instalment invoices?

Yes. Both advance invoices (from the financial planning) and invoices based on a progress claim are locked as soon as they appear in an overview of instalment invoices.

Can I undo the lock via 'Undo'?

No. This lock is tied to the use in the overview of instalment invoices, not to the general lock function for documents. Remove the instalment invoice from the overview to be able to edit it again.

Where can I read more about instalment invoices?

Updated on: 08/09/2026

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