At ASD Solutions, a custom software development company based in Madrid, we build for law firms across Spain the pieces their practice management software does not cover: client intake, document generation, time tracking or a client portal, connected by API to the software they already use. Each piece costs between €1,500 and €8,000 and is delivered in 3 to 6 weeks, at a fixed price excluding VAT. If your firm has few users and works in general practice areas, we will recommend standard software.
Most small law firms do not need to build anything: a good practice-management program handles matters, calendar, deadlines and billing for a reasonable monthly fee. The trouble starts when the firm grows or specialises and begins running daily work on spreadsheets, shared folders and forwarded emails. This article separates which parts of a law firm's work you should buy, which are worth building and how they fit together, along with what you need to know about LexNET, Verifactu, GDPR and professional secrecy before deciding.
What does a law firm's software actually need to handle?
Before comparing programs, write down what the firm does every week. Almost every firm has the same pieces: client intake (first consultation, conflict check, engagement letter and retainer), matter management with its documents and communications, procedural deadline tracking, filing documents with the courts and receiving notifications, drafting from templates, time recording and, at the end of the chain, billing and collection.
Each piece has a different answer. Some are thoroughly solved by standard software and there is no point reinventing them. Others depend so much on how each firm works that generic software only half covers them, and the gap gets filled by hand. The useful decision is not buy or build for the whole firm, but piece by piece, the same approach we take in management software for SMEs: when to buy and when to build.
When is a standard practice-management program enough?
The Spanish market has several mature practice-management programs for law firms, cloud and desktop, with matters, calendar, deadline calculation, fee notes and email integration. Indicative fees range from a few tens of euros per user per month on basic plans to considerably more on plans with advanced modules. Ask for pricing in writing, because it varies widely between vendors and plans.
Standard software wins when the firm has few users (up to 8 or 10), works in general practice areas and its processes look like those of any other firm its size. In that scenario custom development makes no economic sense: you would be paying to build something that already exists, is proven and gets updated when regulation changes. The honest advice for a 3-lawyer firm handling civil and employment cases is to pick the program carefully, migrate the data properly and spend a few weeks configuring it.
The signs that standard software is falling short are different: the same data is typed in three places, deadlines are tracked in a parallel spreadsheet because nobody trusts the program, partners do not know how many hours went into a matter until the fee note is issued, or clients email several times a week to ask how their case is going.
What is LexNET and can it be integrated with custom software?
LexNET is the Spanish Ministry of Justice platform for the secure exchange of filings, documents and notifications between legal professionals and the courts. It is a transport channel, not a management tool: the filing is prepared in the firm's own tools and submitted through LexNET, and notifications arrive the same way. Lawyers access it with their digital certificate, usually the one issued by the bar.
On integration, according to documentation published by the Ministry itself, LexNET exposes web services authenticated with the professional's certificate so that practice-management applications can query and download information. To build that connection, the development team must request access to a Ministry test environment and, once the integration is validated, apply for approval (homologación). So it is possible, but it is not a connector you switch on in an afternoon: there is an administrative process and a timeline the developer does not control.
In practice we advise against having a custom build replace the LexNET connection an approved program already provides. The sensible approach is to let the standard program keep handling that part and connect your own tools to the program (via API or export) to reuse the notifications and deadlines it has already recorded. Pursuing approval only makes sense if the firm has enough volume and a clear reason not to depend on a third party.
Which pieces justify custom development in a law firm?
Client intake is the first candidate. A form of your own that captures the matter details, runs a conflict check against the firm's database, generates the engagement letter and quote, and requests the retainer with a payment link saves hours every week and avoids poorly documented engagements. Standard programs usually start once the client is already registered; everything before that stays in email.
The second is document automation. If the firm works with repetitive models (debt claims, eviction suits, traffic fine appeals, contracts), a generator that fills your own templates with matter data and applies the right variants cuts errors and time. The third is the client portal: a space where clients see the status of their matter, upload documents and download invoices instead of asking by email. The fourth is time recording connected to billing, when the firm bills by the hour or by milestone and wants to see real profitability per matter and per client.
A typical case: a 12-person firm specialising in banking claims keeps its practice-management program for matters, deadlines and LexNET, and adds three pieces of its own on top, connected by API: intake with conflict checks, claim generation from templates and a client portal. It is the same reasoning we lay out in business process automation with custom software: automate what repeats and sets you apart, not what already works.
What does Verifactu change for law firm billing?
Verifactu is the Spanish Tax Agency system requiring billing software to produce chained, tamper-proof records with a QR code, with the option of sending invoices to the Tax Agency in real time. After the postponement approved by Royal Decree-law 15/2025, published in the BOE on 3 December 2025, the dates are 1 January 2027 for corporate income taxpayers and 1 July 2027 for everyone else, including self-employed professionals. Until then it is voluntary. Businesses on the SII system are excluded.
For a law firm this has a direct consequence: billing is the piece where custom development makes the least sense. If your practice-management or billing software is already adapted, your custom tools should pass it the data (hours, milestones, retainers) and let that certified software issue the invoice. Building your own billing system means complying with the technical regulation and maintaining it as it changes, a cost that almost never pays off for a law firm. If you are unsure whether your specific situation is affected, check with your tax adviser.
How do you protect GDPR, professional secrecy and private AI?
A law firm processes data about clients and third parties that is often especially sensitive: health, criminal records, financial or family situation. On top of GDPR and Spain's LOPDGDD, the General Statute of the Spanish Legal Profession requires lawyers to keep professional secrecy. Technically, that means per-matter permissions, encryption, access logs, tested backups, servers in the European Union and data processing agreements with every vendor. There is a practical list in GDPR and security for web applications: a business checklist.
A frequent clarification: Spain's National Security Framework (ENS) applies to the public sector and to private companies providing services to public administrations. A private law firm that does not provide that kind of service is not required to be certified, although its measures are a useful reference.
AI works the same way. Pasting a contract or a filing with client data into a public chatbot raises obvious confidentiality problems. The alternative is private AI, deployed on your own servers or in a European cloud under contract, that summarises documents, finds clauses or compares versions without the data leaving the firm's perimeter. We cover it in private on-premise AI for regulated industries. Always as support for the lawyer's review, never as a replacement.
Buy, build or hybrid? A decision framework with indicative costs
Standard only: firms with up to 8 or 10 users, general practice areas and no high-volume repetitive processes. Cost: the program's subscription plus a few weeks of configuration and migration. It is the right answer for most small firms.
Hybrid: the standard program keeps handling matters, deadlines, LexNET and billing, and one or more custom pieces are added and connected by API. A specific module (client intake, document generator or time recording) usually falls between €1,500 and €8,000 depending on scope, and a full client portal somewhat more. Typical timeline: 3 to 6 weeks per piece. It is the option that best balances risk and cost for firms of 10 to 50 people or highly specialised practices.
Fully custom: only when the firm has a way of working no program covers, for example a mass litigation firm handling thousands of nearly identical matters, and the volume justifies the effort. It starts at €15,000 and takes 2 to 4 months, plus maintenance. Even then we recommend keeping billing and LexNET in certified or approved software.
Before deciding, a €190 technical audit reviews what your current program covers, which API it offers and which piece is worth building, with a diagnosis in 72 hours and a report in 5 business days, deductible if you then hire us. We work from Madrid and remotely across Spain, with our own senior team, two-week sprints and 30 days of support after delivery.
Frequently asked questions about software for law firms
What software does a small law firm need?
For a firm of up to 8 or 10 people in general practice areas, a standard practice-management program is usually enough: matters, calendar, deadlines, fee notes and LexNET connection. Custom development makes sense when high-volume repetitive processes appear or when work is being done outside the program in spreadsheets and email.
Can LexNET be integrated into custom software?
Yes, but it involves a formal process. According to Ministry of Justice documentation, LexNET offers web services authenticated with the professional's certificate, and the developer must request access to a test environment and then apply for approval. In most cases it is more practical to let the approved program keep handling LexNET and connect your custom tools to that program.
When does Verifactu become mandatory for a law firm in Spain?
Following Royal Decree-law 15/2025, on 1 January 2027 for firms subject to corporate income tax and on 1 July 2027 for self-employed lawyers and other taxpayers. Businesses on the SII system are excluded. Before those dates it is voluntary. Confirm your specific situation with your tax adviser.
How much does custom software for a law firm cost?
It depends on scope. A specific piece on top of the program you already use (client intake, document generator or time recording) usually costs between €1,500 and €8,000 and is delivered in 3 to 6 weeks. A fully custom system starts at €15,000 and takes 2 to 4 months. Maintenance is contracted separately, from €500 a month.
Can lawyers use artificial intelligence with client documents?
Carefully. Uploading documents with client data to a public AI service can compromise professional secrecy and GDPR compliance. The recommended approach is private AI deployed on your own servers or in a European cloud with a data processing agreement, used to support the lawyer's review and never to replace it.
