Establish the baseline and the payment evidence
Record the accepted contract version, included quantities and products, IVA treatment, exclusions and provisional items. Agree what each acconto or progress payment is for. A calendar date alone does not establish that a construction milestone has been completed; define the evidence, responsible reviewer and invoice process.
For a private renovation, SAL means a record of progress in the agreed contractual arrangement. Do not import a public-contract payment rule or a tax-incentive percentage into every domestic job. Describe the measurement or milestone, the cumulative amount, earlier payments and the new amount requested. Keep the contractor’s record and your payment receipt linked without treating them as the same event.
Read cumulative SAL without adding it twice
| Stage | Cumulative amount | Earlier payments | New payment | Status |
|---|---|---|---|---|
| Acconto | 8 800 | 0 | 8 800 | Paid |
| SAL 1 | 22 000 | 8 800 | 13 200 | Paid |
| SAL 2 | 33 000 | 22 000 | 11 000 | Paid |
| Final reconciliation | 45 540 | 33 000 | 12 540 | Due, subject to agreed close-out |
After SAL 2, the actual payments are €8,800 + €13,200 + €11,000 = €33,000. The cumulative €22,000 and €33,000 are not extra invoices to add again as cash. Confirm whether the contractor’s document is an accounting statement or tax invoice, and how advance invoices are deducted in the final invoice. Use the supplier’s actual invoice reconciliation rather than issuing your own tax correction.
Authorise the change and its price
Civil Code article 1659 concerns contractor changes, written evidence of authorisation and the effect of a globally agreed price. Before an optional extra is ordered, record the changed scope, reason, price basis, tax, effect on timing and explicit agreement to any extra compensation. Approval of a different drawing should not leave the price unspecified.
- A genuinely additional gross task adds its accepted amount.
- A cancelled included task removes its agreed credit.
- A new selection replacing an allowance adds only the difference after the old allowance is removed.
- A provisional sum replaced by a firm price is removed from uncertainty as the approved work is added.
Necessary changes, disputed work and urgent protective action need their own contractual and professional assessment. Record what was observed and refer the affected work to the right person. A reserve is a funding choice, not automatic authorisation for the contractor to spend it.
Reconcile the current contract and whole-project forecast
| Item | Amount |
|---|---|
| Original contract including assumed IVA | 44 000 |
| Accepted additional work | 1 650 |
| Agreed credit for cancelled work | −550 |
| Replacement: new 1 320 less included 880 | 440 |
| Current agreed contract | 45 540 |
| Recorded payments to contractor | 33 000 |
| Unpaid part of current contract | 12 540 |
| Owner purchases outside contract | 6 100 |
| Professional invoices outside contract | 2 600 |
| Unresolved-work allowance, not yet contracted | 1 400 |
| Chosen unallocated reserve | 3 000 |
| Whole-project funding forecast | 58 640 |
| Cash still needed after recorded contractor payments | 25 640 |
The forecast is €45,540 + €6,100 + €2,600 + €1,400 + €3,000. Its €25,640 cash remainder assumes the owner purchases, professional invoices, unresolved allowance and reserve have not yet been paid or used. If any is paid, record it and subtract it once from cash still needed. The agreed contract remains €45,540; payments reduce the unpaid balance rather than the contract price.
If the €1,400 unresolved allowance becomes an approved €1,100 task, replace it: forecast funding becomes €58,340 with reserve unchanged. Adding €1,100 while leaving the whole €1,400 unresolved would exaggerate the same exposure.
Keep tax documents and funding on separate tracks
Ask for net amount, applicable IVA and gross value on each accepted change. The agency guide distinguishes IVA relief, renovation deduction conditions and required payment evidence. Use the appropriate bank-transfer method where required and preserve executed receipts; do not use an expected future IRPEF deduction to reduce the money needed for a current invoice.
A changed work package can also affect the design, building submission or the site-safety arrangements. Send the relevant decision to the tecnico and safety professional before the affected work proceeds. Your commercial change register does not replace their formal documents.
Review the forecast at each agreed checkpoint
- Match completed work to the agreed milestone and reviewer’s evidence.
- Reconcile the new invoice with earlier advances and actual transfers.
- Check that every accepted change includes its price, tax and any credit.
- Replace resolved allowances rather than stacking them with firm costs.
- Compare the next payment dates with available funds and remaining reserve.
- Prepare final reconciliation and handover under the contract.
Civil Code article 1665 concerns checking, acceptance and payment, subject to the relevant agreement. Plan that final step instead of assuming that either a fully paid invoice or a withheld balance resolves all defects. Record the agreed payments and project notes in Reno Pro, keeping the signed contract, SAL evidence and tax documents as the supporting record.
Sources, date and scope
- Normattiva — Codice civile, art. 1659
- Agenzia delle Entrate — Ristrutturazioni edilizie: le agevolazioni fiscali, febbraio 2026 — copia PDF
- Normattiva — Codice civile, art. 1665
- Normattiva — D.Lgs. 81/2008, art. 90
Checked on 19 October 2026. Examples concern a flat in Milan unless stated otherwise; check the actual work against the rules of your comune and region. Teaching figures are invented to explain the accounting, not market averages or an offer. Appropriate professionals establish tax eligibility, technical suitability and required filings. Where used, the February 2026 Agenzia delle Entrate guide is linked as a copy of the agency-authored document.