How to automate billing at your law firm

At a law firm, the road between doing the work and getting paid is longer than it looks. First you have to remember everything that was done. Then you have to turn it into a correct invoice, with the client’s tax details right and the legal requirements met. Then you send it, wait, and — far too often — chase. Every step adds friction, and all friction ends the same way: hours worked that never reach an invoice, and invoices issued that take months to collect.

Automating billing doesn’t mean a program decides what you charge. It means removing friction from that road: work gets recorded as it happens, the invoice comes out of the matter without retyping anything, it complies with the rules without you having to think them through each time, and collection is chased systematically instead of depending on someone remembering.

Record the work as it happens, not at month end

The first leak isn’t in the invoice — it’s weeks earlier, in the work nobody wrote down. On the last day of the month, someone at the firm sits down with the calendar, the email and their memory, and tries to reconstruct what was done for each client. What isn’t remembered isn’t billed. And what’s half-remembered gets billed low, because when in doubt nobody wants an argument with the client.

The alternative is to capture work in the moment: a time entry when you hang up the call, a fixed fee when the filing goes in, the provision of funds recorded the day it’s agreed. You don’t need to stopwatch every minute; you need every meaningful action to leave an entry on its matter, with a date and an author. The month-end invoice stops being an exercise in archaeology and becomes a review of what’s already there.

This holds for all three common fee models: hourly, where the entry is the hour itself; fixed fee, where the entry is the milestone reached; and retainer, where what you record is what falls inside and outside the agreement. In all three cases the rule is the same: the data is born where the work is born.

The invoice is born from the matter

If billing lives outside the matter — a Word template, an Excel sheet holding the invoice series — every invoice means copying concepts, amounts and tax details by hand. Every copy is a chance to get it wrong: the client’s old tax ID, a forgotten line, transposed digits. And when the client questions an item, someone has to reconstruct where it came from.

When the invoice is generated from the matter, all of that disappears. The line items are already recorded, the client’s tax details are already on their record, and the invoice is the final step of a process rather than a document manufactured on the side. Better still, anyone at the firm can answer “why was this billed?” by looking at the matter, without depending on whoever issued the invoice.

What the law requires of your invoices in 2026

This is where Word and Excel have stopped being an option. The VeriFactu regulation (Royal Decree 1007/2023, with deadlines set by RD 254/2025) is already in force: since 1 January 2026 for corporate income tax payers, and since 1 July 2026 for everyone else, including self-employed professionals. Whatever legal form your firm takes, it is already inside the calendar.

In practice, VeriFactu requires invoices to be issued with software that produces billing records meeting the regulation’s technical requirements — unalterable, chained and verifiable. A loose document made in a word processor doesn’t qualify. If your firm still invoices that way, this is the concrete, decree-numbered reason to change. Our VeriFactu guide for law firms has the full detail.

On taxes, the general rules are well known: legal services carry VAT at 21 %, and when you invoice companies or other professionals as an individual practitioner, IRPF withholding applies — 15 % as the general rate, or the reduced 7 % for new professionals during their first years of activity. These are the general rules, not an opinion on your case: the particulars (exempt transactions, clients outside Spain, your corporate form) are for your tax advisor to confirm.

And one honest note about what’s coming: Law 18/2022 (Crea y Crece) will make electronic invoicing mandatory between businesses and professionals, but its implementing regulation is still pending and the clock has not started, so today it belongs on your radar, not on tomorrow’s to-do list.

Provisions of funds and advance payments

Provisions are the part of billing where most firms improvise. The useful discipline is simple: ask for the provision before starting, document it — how much, what for, what it will be applied against — and deduct it visibly on the final invoice, so the client can see the money’s full journey.

For tax purposes, not everything that comes in up front is the same: an advance on fees and a provision earmarked for disbursements — amounts you pay on the client’s behalf — are treated differently for VAT. The operational rule is to record every incoming amount with its correct nature from day one, and let your advisor confirm the treatment of each type. Judgement can’t be automated; making sure every provision is noted on its matter, where nobody loses sight of it, can.

Collecting without becoming a debt collector

The most uncomfortable part of billing is chasing. Because it’s uncomfortable, it gets postponed; because it gets postponed, you get paid late. The fix is not more personal firmness — it’s a system that doesn’t depend on anyone’s mood.

Three rules are enough. First: every invoice goes out with a clear due date and an easy way to pay. Second: reminders follow a fixed schedule — before the due date, on it, and at regular intervals afterwards — in a cordial tone that never changes, because the firm sends them, not a lawyer squirming at the awkwardness. Third: someone reviews the list of outstanding invoices every week, ordered by age, because what isn’t looked at doesn’t get collected.

Month-end close and your accountants

The end of the circuit is handing clean data to whoever keeps your books. A healthy month-end close means an invoice series with no gaps, all the month’s invoices in one place, payments reconciled against their invoices, and provisions identified as what they are. If your gestoría receives that, their work — and their bill — shrinks; if they receive an ambiguous spreadsheet and three loose PDFs, you pay for it in time and in errors.

How Mandato solves it

In Mandato, billing lives inside the matter: the time entries, fees and provisions noted on the case become the lines of the invoice, without retyping. Invoices are issued VeriFactu-compliant out of the box, with no separate setup, so the RD 254/2025 calendar stops being your problem.

And for the close, Mandato syncs with Holded, so your accounts receive the invoices without manual exports and your accountants work on data that arrives already in order.

Start with the weakest link

You don’t need to rebuild the whole circuit at once. Look at where your firm loses the most — unrecorded work, invoices slow to go out, collections nobody chases — and fix that link first. A firm’s billing doesn’t improve through month-end heroics; it improves when the road from work to payment has so little friction that following it is simply the normal thing to do.