Setting payment terms, instalments and due dates on a sales invoice in SamBooks

How to decide when and how a customer pays a sales invoice: the "Payments and due dates" block, instalments, the account the money lands on, and what happens if you leave it blank.

What this covers

Every sales invoice has a Payments and due dates block, on both the creation and edit form: here you decide whether the customer pays in a single instalment or several, with which payment method (cash, bank transfer, direct debit…) and into which company account the amount should arrive. This feeds the FatturaPA electronic invoice trace (the DatiPagamento block) and, once transmitted to the SDI (the Italian tax exchange system), generates the open items in the Due-dates register (Scadenzario).

This guide covers how you set up the payment plan on the invoice itself: the fields on each instalment, the liquidity account, amount matching, the TP01/TP02/TP03 conditions, and what happens if you specify nothing. It does not cover what you do once a due date exists: to record a collection see Record a collection or a payment, for aging see The open-items due-dates register, for a late customer see Chase a customer for an overdue invoice.

Before you start

• You need a role with write access on invoices — Gestore (full-access manager) or Amministrativo.
• If you want the bank transfer to land on a specific account, that account must already exist under Banking, ideally with its IBAN filled in.
• If the selected customer has a default liquidity account on file, the first instalment you add inherits it automatically: not required beforehand, but it saves a step.

Step by step

1. Open "Payments and due dates" on the invoice form

In Sales invoices → New invoice (or when editing a draft or Ready invoice), below the lines and the closing discount you'll find the "Payments and due dates" section. It's the same editor used by the purchase invoice and the pro-forma invoice: on the sales invoice the account is chosen from a directory of company accounts, while on the purchase side it's the supplier's IBAN typed by hand.

With no instalments added, you'll see "No due date: a single due date at the document date will be created." — that's the default behaviour, explained in step 6.

2. Add an instalment: the fields

Press "Add due date": a card opens with four fields.

• Due date — the date the instalment is due by. Optional: if left blank, SamBooks still computes a fallback date, but only when the invoice is emitted (see step 6).
• Amount — required. An instalment left at zero isn't considered filled in.
• Method — required: the FatturaPA ModalitaPagamento code (MP01-MP23). The most common are Cash (MP01), Bank transfer (MP05), Payment card (MP08), Direct debit / RID (MP09), SEPA Direct Debit (MP19) and PagoPA (MP23). The full list is in the selector, shown with its official description next to the code — these still appear in their Italian regulatory wording, since they're the official tax-authority descriptions.
• IBAN (in practice, an account — see step 3).

Every instalment has its own "Remove due date" button, to drop it without touching the others.

3. Pick the liquidity account, not a free-text IBAN

On the sales invoice this field isn't a free-text IBAN box: it's the "Select liquidity account" picker, drawing on the financial accounts already on file under Banking (with a "None" option). SamBooks derives the IBAN, BIC, bank and account holder from that account — never a hand-typed IBAN. If the customer has a default account on file, the first instalment inherits it automatically; later instalments start blank until you fill them in.

An account with no IBAN can still be picked — this happens with an account like Stripe, which can still receive a bank transfer sent separately — but if the chosen method requires one (bank transfer MP05, bank slip MP07, RIBA MP12, MAV MP13, postal slip MP18: methods the trace classifies as paid into an account of yours) a warning appears:

"This account has no IBAN: bank transfer (and similar) payments need a liquidity account with an IBAN, otherwise the invoice will stay a draft and cannot be sent to SDI. Add an IBAN to the account under Settings → Banking, or pick a different account here."

Other methods (direct debit, fast direct debit, bank or postal standing order, SEPA Direct Debit) draw from the customer's account, not yours: for those the account here isn't required. An account with no IBAN is the single most common reason an invoice stays stuck: full list in Resolve missing required data.

4. Several instalments: matching the total, and same-day merging

Already with a single instalment filled in (amount greater than zero) an "Instalments total" line appears below the list, the live sum; with more than one it's the same sum, spread across more rows. If it doesn't match the invoice total (within one cent per instalment), the figure turns red and a warning is pinned under the totals:

"Instalments do not match the document total — Instalments add up to {somma} but the document is {totale} (difference {differenza}). Fix the amounts, or remove the instalments to leave a single due date for the document total."

Saving stays blocked until you fix it, and the server enforces the same check: it can't be worked around through another path (a direct API call, or Sam). One known exception: on an invoice to a Public Administration customer under split payment, the server also accepts a plan that adds up to the total net of the split-off VAT (paid by the customer directly to the tax authority), but the form doesn't know about that alternative total and may flag a genuinely correct plan as mismatched — an interface limitation, not a mistake on your part.

If two instalments fall on the same date, they don't produce two separate open items: once emitted, SamBooks merges them into a single due date, adding the amounts (keeping the method, IBAN and payee of the first). That's not a defect: it's a deliberate product rule — two identical due dates on the same day are still a single instalment, split across two rows of the trace.

5. Payment conditions (TP01, TP02, TP03)

The DatiPagamento block also carries an overall payment condition: TP01 (instalment payment), TP02 (payment in full) or TP03 (advance payment). On the sales invoice, SamBooks doesn't currently expose a selector for it: on a new invoice, as soon as you fill in at least one valid instalment, the document is automatically flagged TP02, regardless of how many instalments there are or whether it's an advance payment. If you edit an invoice that already carries a different condition (set from another source), it's carried forward on every save as long as at least one instalment remains — it doesn't revert to TP02 just because you fix an amount or a date, and is only lost if you clear the plan entirely. Any payment terms the customer has on file are not read by this form: only the instalments you fill in here count.

6. What happens if you specify no instalment at all

An invoice with no instalment sends no DatiPagamento block: nothing visible happens on save. Only when the invoice is emitted — transmitted to the SDI, or generated internally for a reverse-charge self-invoice — does SamBooks create a single due date for the whole total:

• if the selected customer has payment terms on file (a number of days combined with "invoice date" or "end of month"), the due date uses them;
• otherwise the due date matches the document date — immediate payment.

The calculation happens once, at the point of emission: changing the customer's terms on file afterwards doesn't move due dates that already exist.

7. Where it all lands: the due-dates register is created only after sending to SDI

In the vast majority of cases, an invoice in Draft or Ready status has no real due date yet: the plan is saved on the document, but it only becomes an open item once transmitted. One exception: when the collection arrives BEFORE the document, an invoice linked to a Stripe payment already collected (stays "Ready", pending review) or a pro-forma advance already collected (created as a draft with the collection already on it) carries an open due date from the start. On the invoice detail, "Document" tab, the "Payments & due dates" card shows the payment condition plus a table with Due date · Amount · Outstanding · Method · IBAN · Status; for an ordinary draft or Ready invoice you'll only see "No due dates recorded". Every row with an outstanding balance greater than zero also carries "Record receipt" — usually only after sending to SDI, since that's when due dates are created — the same flow as Record a collection or a payment. If credit or debit notes are linked to the invoice, the outstanding balance already accounts for them ("Linked credit notes: −{importo}" / "Linked debit notes: +{importo}"): how those are generated is covered in Issue a credit note and Issue a debit note.

For the full list of open due dates, filterable, with aging, see The open-items due-dates register.

8. Editing the plan on an invoice you've already saved

As long as the invoice stays in Draft or Ready status (not yet sent to SDI), reopen it with "Edit": the editor shows the document's real instalment plan, not an empty section. You can add an instalment, correct an existing one, or remove one — not only add. A note under the editor spells it out:

"These are the document's own instalments: on save they replace the payment plan and regenerate the schedule. Instalments already collected are kept."

In practice: whatever is on screen the moment you press "Save changes" becomes the plan saved on the document, including any rows you deleted. For nearly every Draft or Ready invoice this doesn't touch any real due date, because — as in step 7 — none exists yet: saving only updates the plan stored on the document, which becomes real open items once transmitted. In the rare case of an already open, collected due date (the "advance collection" exception from step 7), that row stays exactly as it is: saving the plan doesn't touch it.

If something goes wrong

• "Fill in method and amount for every instalment, or remove it." — you started filling in an instalment (for instance, picked only the date) without finishing it: complete method and amount, or drop it with "Remove due date".
• "Instalments do not match the document total" — the sum of the instalments doesn't match the document total beyond the one-cent-per-instalment tolerance: fix the amounts or remove instalments.
• The warning about an account with no IBAN — you picked a method that requires an account of yours (bank transfer and similar) on an account with no IBAN: add the IBAN to the account under Banking, or switch accounts here.
• The invoice doesn't show up in the due-dates register — normal while it's Draft or Ready: the due date is usually created only on transmission (exceptions: a linked Stripe payment already collected, or a pro-forma advance already collected).
• You can't find where to pick TP01/TP02/TP03 — there's no dedicated field on the sales invoice: the system sets TP02 automatically as soon as there's at least one instalment.

Frequently asked questions

How do I set a 30-day payment term? The simplest route is to fill in no instalment and let SamBooks derive the due date from the customer's payment terms on file (days plus invoice date or end of month), or add a single instalment with the full amount and the date you choose.

How do I split an invoice into several instalments? Press "Add due date" once per instalment, filling in date, amount and method for each. The sum must match the document total, within one cent per instalment.

Where do I put the IBAN on the invoice? You don't type it: pick the liquidity account from the instalment's selector. The IBAN, if that account has one, is derived from there.

Which payment method do I pick for a bank transfer? MP05 - Bank transfer. With that selected, the chosen account needs an IBAN, or the invoice stays blocked before it can be sent to SDI.

Why doesn't the invoice show up in the due-dates register? Because it hasn't been sent to the SDI yet: due dates are usually generated only on emission (a collection that arrived before the document — a linked Stripe payment, or a pro-forma advance — is the exception).

How do I mark an invoice as paid? From the "Document" tab, the "Record receipt" button on the due-date row — appears with an outstanding balance, usually after sending to SDI — or from the due-dates register. Details in Record a collection or a payment.

Can I put two instalments on the same day? You can enter them, but on emission SamBooks merges them into a single due date for the sum of the two amounts: you'll never find two open items on the same date for the same document.

What happens if I specify no due date? On transmission a single due date is still created for the full invoice total, dated from the customer's payment terms on file or, failing that, from the document date.

What is TP02? The FatturaPA "payment in full" condition — the one SamBooks assigns automatically to every new invoice with at least one instalment, because there's currently no way to choose a different one from the form.

How do I link a bank account to the invoice? By selecting it from the liquidity-account field of each instalment: if the customer has a default account on file, the first instalment proposes it on its own.

Related guides

• Record a collection or a payment — what to do once the customer pays.
• The open-items due-dates register — the full list, filters and aging.
• Chase a customer for an overdue invoice — what to do about a late payment.
• Resolve missing required data — the case of an account with no IBAN.
• Create a sales invoice — the rest of the invoice form.
• Issue a credit note and Issue a debit note — the effect on an invoice already partly paid.