Revolving Credit Card Interest Simulator

Data verified for 2026 · Last verified: August 29, 2026Official sources: Bank of Spain· BOE

Used Credit Amount (€)

Monthly Payment Fee (€)

Annual nominal interest rate — TIN (%)

Contract APR / TAE (%) The APR (TAE) includes compounding frequency and certain costs, used here only as an orientative reference. Debt simulation uses the nominal rate (TIN).

Complete Legal and Financial Guide to Revolving Credit Cards in Spain

Revolving credit cards are flexible credit facilities where the available line of credit is automatically renewed as debt is repaid. However, due to high nominal interest rates (TIN often exceeding 20% to 26%) and minimum payment structures, cardholders frequently experience indefinite debt prolongation where payments barely cover accrued interest.

In Spain, revolving contracts are subject to strict scrutiny under the Usury Act of July 23, 1908 (Ley Azcárate) and Supreme Court landmark rulings (STS 149/2020, STS 258/2023, SSTS 154/2025, and SSTS 155/2025).

Supreme Court Usury Doctrine: The 6-Point Margin Rule (STS 258/2023)

Under Spanish Supreme Court case law:

Contemporaneous Comparison: The contractual APR (TAE) must be compared with the specific average TEDR rate published in Chapter 19 (Table 19.4) of the Bank of Spain Statistical Bulletin for revolving cards at the exact contract date.
The 6 Percentage Points Standard: In STS 258/2023, the Supreme Court established that usury occurs when the contract rate exceeds the official market average by more than 6 percentage points (600 basis points).
Contracts Prior to June 2010: Evaluated against the earliest revolving benchmark (2010 annual average: 19.32% TEDR), with an orientative adjustment of +0.20 to +0.30 points to reconcile TEDR to TAE.

Transparency and Abusive Terms Controls (SSTS 154/2025 & 155/2025)

In addition to usury, revolving credit clauses are examined under general contracting terms (LCGC) and consumer protection (TRLGDCU) laws. The Supreme Court established that failure of transparency does not mean automatic nullity; courts evaluate whether the terms (capital recomposition, anatocism, minimum fee compounding, and pre-contractual disclosures) are substantively unfair to the consumer.

Legal Effect of Judicial Nullity (Article 3 Usury Act)

When a revolving agreement is judicially declared void due to usury, the consumer is only required to return the actual net principal drawn. The lending institution must refund all paid interest, renewal fees, late payment penalties, and mandatory insurance premiums that exceed that net principal.

Practical Example

Example 1: The Minimum Fee Indefinite Debt Trap

Input: Drawn Debt: 3,000.00 € | Monthly Fee: 60.00 € | Rate: 24.00% TIN

Output / Result: Amortization Horizon: Over 12 years | Total Interest Paid: Exceeds 3,800.00 €

At 24% TIN, monthly interest is 60.00 € on 3,000 €. A 60.00 € payment barely covers the interest, resulting in near-zero principal reduction.

Example 2: Judicial Usury Comparison Check

Input: Contract Date: 2018 | Contractual APR (TAE): 27.24% | 2018 BoS TEDR: 19.98%

Output / Result: Difference: +7.26 percentage points (> 6.00 points threshold)

Because the difference exceeds 6 points over the official Bank of Spain benchmark, the interest rate matches the legal criteria for usury under STS 258/2023.

How to Simulate & Analyze a Revolving Credit Card in 4 Steps

Enter Used Credit Balance

Type the total outstanding credit balance drawn on your revolving card.

Set Monthly Repayment Fee

Enter the fixed monthly payment amount currently being charged on your bank receipt.

Indicate Contractual Interest Rates (TIN / APR)

Input the nominal interest rate (TIN) and optional contract APR (TAE) shown in your contract.

Review Payoff Schedule & Usury Analysis

Inspect total interest paid, estimated months to payoff, and judicial case law benchmarks under Supreme Court rulings.

Frequently Asked Questions about Revolving Cards in Spain

When is a revolving credit card interest rate legally considered usurious in Spain?

Under Spanish Supreme Court case law (STS 149/2020 and STS 258/2023), usury is established when the contractual APR (TAE) exceeds the specific average TEDR rate published by the Bank of Spain for credit cards and revolving credit at the contracting date by more than 6 percentage points. There is no universal fixed threshold (such as an automatic 26%).

What reference rate applies to revolving contracts signed before June 2010?

For contracts signed before June 2010 (when the Bank of Spain began publishing dedicated revolving statistics), case law applies the closest contemporaneous reference from 2010 (19.32% TEDR) with an orientative adjustment of +0.20 to +0.30 percentage points (+20 to +30 basis points) rather than general consumer loan indices.

What financial consequences occur if a revolving card is declared null for usury?

Pursuant to Article 3 of the Spanish Usury Act of July 23, 1908 (Ley de Represión de la Usura), the contract is declared radically null. The borrower is only obligated to repay the principal actually drawn, and the financial institution must refund all interest, commissions, insurance, and fees paid that exceed that principal.

Why does a low monthly payment prolong revolving debt indefinitely ("infinite debt trap")?

Because when a minimum monthly fee is selected (e.g. 50 € on a 3,000 € balance at 24% TIN), almost the entire payment goes toward monthly interest and fees, leaving only a few euros to amortize the principal. If new purchases are made, the debt increases and compounds over decades.

What are the transparency and unfairness controls under Supreme Court rulings SSTS 154/2025 and 155/2025?

Beyond usury, revolving terms are subject to transparency and unfairness controls. Under rulings SSTS 154/2025 and 155/2025 (reiterated in 2026 by STS 367/2026), lack of transparency alone does not automatically create nullity: judges must evaluate whether non-transparent terms are abusive, analyzing capital recomposition, compound interest, misleading debt presentation, and pre-contractual disclosures.

Revolving Credit Card Simulator