How do you compare three renovation quotes on the same basis?

Send one brief to every bidder

Prepare the same drawings, scope and decision list for everyone. Define the work by room and package, with quantities and product specifications where known. Mark unresolved issues explicitly. A contractor should know whether it is pricing a complete installation, a supply allowance or an investigation followed by a revised price.

Spanish quotations often use partidas for cost items, mediciones for measured quantities and calidades for the specified product or finish quality. Those headings only help if the content is precise. “Good quality tiles” does not establish the model, supply price, dimensions, installation pattern or edges. Ask for a written answer rather than filling a gap with your preferred interpretation.

Build a comparison from boundaries

Keep technical alternatives in a separate column. A different substrate repair or ventilation proposal may be a valid improvement, but it is not the same scope at a different price. Ask the relevant professional whether the alternative meets the intended performance before accepting a cost advantage.

Normalise the tax presentation

Consumer law article 60 requires the relevant price information before contract. Distinguish “IVA incluido” from a net quotation and identify which outside costs remain yours. Where the price cannot be fixed yet, ask for the calculation method and the event that will establish it.

Use AEAT’s renovation rules to check any claimed reduced rate with the contractor. Compare the correct gross payable amounts, even if legitimate tax treatments differ. Do not apply 10% to every labour line by habit: the AEAT FAQ addresses the material threshold and artificial division of one operation. An unexplained low tax rate should be a question, not a competitive advantage you assume will survive invoicing.

Three offers after written clarification

B’s headline €27,225 includes €4,725 IVA on €22,500. Its €500 net correction adds €605 gross. A’s €2,000 net correction adds €2,420 gross. After clarification A and B cost the same for the defined brief; C is €605 higher. The comparison has removed a misleading gap without proving which company will deliver best.

Treat unknown allowances honestly

Ask what a provisional sum covers, whether it includes materials and labour, its IVA basis and how the actual amount replaces it. Specify the contractor’s mark-up or coordination charge if one applies. An undefined allowance cannot be made reliable by choosing a round number yourself.

If the route of a concealed drain remains unknown, show it as unresolved in all three offers. Commission an appropriate investigation or agree a written adjustment mechanism before commitment. Your comparison allowance is a funding assumption; it is not a binding price from the contractor. Keep confirmed offers and editorial estimates visibly different.

Compare the agreement as well as the sum

• Company identity, contact details and relevant authorisations for regulated installation work.
• Who supervises and who actually carries out each trade.
• Start conditions, completion programme and product decision deadlines.
• The process for substitutions, extra work and recording delays.
• Payment triggers, invoice detail and how advances are credited.
• Insurance, responsibility for damage and the route for resolving defects.

The Madrid consumer guidance explains the written-budget and invoice record; OCU’s practical advice also supports keeping those documents. Neither a recommendation nor a membership badge proves the quality of this particular proposal. Ask for evidence of comparable completed jobs and clarify who your contract is with.

Match payments to the agreed exposure

Ask what an advance funds, which products are ordered, who owns them and what happens on cancellation or supplier failure. There is no universal deposit percentage established by this article. A chosen 20% advance against the €27,830 example is €5,566, leaving €22,264 of that contract unpaid; it does not increase the contract to €33,396.

Agree milestones that can be checked and obtain invoices and traceable payment records. If another stage amount is described as cumulative, subtract earlier payments instead of paying that cumulative figure again. Do not accept a contract structure you do not understand merely because the last line is attractive.

Make a decision you can defend

1. Return the same clarification questions to each bidder.
2. Obtain revised written totals and freeze the specification used for selection.
3. Compare price, unresolved risk, delivery evidence and payment exposure.
4. Record why the selected offer meets the brief and what remains conditional.
5. Save the accepted quote, drawings, exclusions and change procedure together.

Use a table or your project records to keep the decision understandable. Reno Pro can help organise planned and recorded costs and subsequent payments. The contractor still confirms its price, and the professional assesses technical choices. A fair comparison ends with a defined agreement, rather than a ranking of three incomplete documents.

Sources, date and scope

• BOE — Real Decreto Legislativo 1/2007: artículos 60 y 60 bis
• Agencia Tributaria — IVA: obras de renovación o reparación de viviendas
• Agencia Tributaria — Preguntas frecuentes sobre obras y reparaciones en inmuebles
• Comunidad de Madrid — Reformas del hogar: presupuesto, factura y reclamaciones
• OCU — Reformas en casa: consejos prácticos, 4 junio 2020

Sources checked on 19 October 2026. Local procedures and examples concern the city of Madrid unless stated otherwise. IVA explanations concern the territory where that tax applies, rather than the separate tax systems of the Canary Islands, Ceuta or Melilla. Original worked calculations are teaching examples for the stated scope, not market averages or contractor offers.