Registering before you start, or waiting for the first invoice

Two registrations, two rules

The question — do I register now or wait until I have a client? — gets answered badly because it is treated as one decision. It is two separate steps, before two different authorities, with two different rules.

Census registration, with the tax authority, goes before the activity begins: you notify that you are going to start, under which business classification and in which tax regimes. RETA registration — the special social security scheme for self-employed workers — corresponds to the day the activity actually begins on a habitual basis, and it can be filed up to sixty calendar days in advance.

One practical note: modelo 037, the simplified version everyone used for years, was abolished by Order HAC/1526/2024 with effect from 3 February 2025. Census registration, amendment and deregistration now all go through modelo 036. If anyone sends you a 037, their information is out of date.

The two positions, side by side

	Register before	Wait for the first invoice
Tax authority	This is what the rule says: census before starting	An invoice is issued without being registered, with no business classification declared
Social security	Registration on the start date, filable up to sixty days in advance	You work without contributing
Immediate cost	The autónomo contribution from the day of registration, and quarterly obligations from day one	Zero, while it lasts
Reduced start-up contribution	Enjoyed from the outset, even before you invoice	Backdated registration does not give access to the reduced contribution for that period
Risk	Paying contributions while there is no income	Registration imposed with retrospective effect, arrears with a surcharge and penalty proceedings
Costs incurred beforehand	Deductible, with recoverable VAT if the start is declared first	They get complicated, and are sometimes lost

What you actually risk by waiting

An invoice issued without registration leaves a trail: your client deducts it and declares it, and there you are. When social security regularises, it does so with retrospective effect to the real start of the activity, claiming the contributions for the period with a surcharge. Those contributions are not the reduced ones: the discounted start-up rate rewards registering on time, not registering late.

At the tax office the problem runs in parallel: an activity not declared on the census, with whatever infringement follows and, if you charged VAT without being registered, the obligation to pay it over regardless. And if you did not charge it, believing no VAT arose without registration, the amount comes out of your margin, because the tax is triggered by the transaction and not by the paperwork.

There is a middle ground that gets abused: the idea that an occasional, low-income activity does not require social security contributions. There is a line of practice, applied for years, that looks at whether the activity is habitual and treats income levels as an indicator — but it is not a written exemption, it is argued case by case, and it does not protect you from census registration, which is required from the very first transaction. Relying on it as a plan is leaning on a defence argument rather than on a rule.

And what moving early costs

• The contribution, from the day you register. It accrues by the day from that date, whether you invoice or not.
• The clock on the reduced contribution starts running. That is the real cost and the one almost nobody calculates: burning months of the flat rate with no income spends the best advantage of the start-up phase in the period where it helps least.
• Quarterly obligations begin even with no income: the returns have to be filed, and filing them at nil is still filing.

So, where there is room, the combination that works best is to have the census side prepared and to set the RETA registration on the real start date, using the sixty days of advance filing to sort the paperwork without rushing but without bringing the contribution forward.

Two situations we see a lot among people who have just arrived

You already have a foreign client and no Spanish structure yet. The temptation is to invoice from a company you still hold in your home country and postpone the Spanish question. That works until it does not: if the work is performed here and you live here, the income is Spanish-source income whatever letterhead the invoice carries, and the structure abroad adds an argument rather than removing one.

You have a start date in a contract but the work has not begun. A signed contract is not the start of an activity, and neither is a first meeting. What starts the activity is offering goods or services on your own account, in a habitual way. The nuance matters because it sets both dates: the census date and the RETA date, which do not have to be the same.

If your clients are abroad, one extra step

Anyone who is going to invoice businesses in other EU countries needs to be on the roll of intra-Community operators, the ROI, and that registration is requested on the same modelo 036 and is not granted instantly. Asking for it at the same time as registering saves a fortnight later: invoicing inside or outside the EU.

The case that fits neither column

The table sets out two clean positions. In practice most people who ask are somewhere in between, and that place appears in neither column.

• The single, isolated invoice. One collaboration, a commission that is not going to repeat. The census registration is required all the same — you declare the start, you invoice, you file the cessation — while the social security contribution is argued through the question of whether the activity is habitual. Registering and deregistering in the same month is a legitimate and frequent step; issuing the invoice without ever having gone through the census is not.
• Holding a job as well. Someone who already has a payslip and starts something on the side usually assumes that those contributions cover them. They do not: the self-employed scheme is independent of the general one, even though mechanisms exist to adjust where contributions are paid twice above certain ceilings. The monthly amount is payable from the first day all the same.
• The activity that started months ago. It is the most repeated enquiry on this page: invoices are already going out, there is no registration, and the real question is not whether to register but how. Coming forward of your own accord, before the notice arrives, changes the picture a great deal: at most it triggers the surcharges under article 27 of the General Tax Act rather than penalty proceedings. It does not guarantee everything, but it is the difference between you arriving and them arriving.
• Letting a property, and other activities that create census and VAT obligations without necessarily meaning registration in the self-employed scheme. Having forms to file does not always mean having contributions to pay, and the reverse is true too.
• Invoicing clients in other countries from day one. Registration as an intra-Community operator is applied for on the modelo 036 itself, and the authorities can take their time over granting it — there is no fixed period you can rely on. Waiting until you have a client before registering can leave you unable to issue that first invoice properly.

One more, common among people who have just arrived: the tax number you already hold is not the same thing as being registered for an activity. A NIE issued for a residence application, or a number obtained in order to buy a flat, says who you are. It does not say that you are in business, and it opens none of the obligations — or the rights — that registration opens.

What to look at before choosing the date

• What was, or will be, the first act of the activity: the first invoice, the first commission accepted, the first purchase made in order to sell. That is the date that gets checked afterwards.
• The heading that matches what you are going to do, and whether it drags withholding or VAT obligations behind it that you were not expecting.
• Costs already paid, and whose name the invoices are in, with the tax number on them.
• Whether you are drawing, or about to draw, unemployment benefit, and how many days are left.
• Whether you have a payslip, and under which scheme it contributes.
• Your forecast net profit for the first year, which is what sets the contribution base and the adjustment that follows the year after.
• Whether you will have clients or suppliers in the European Union from the outset.

How we handle it

We look at three things: when the activity genuinely begins, which earlier costs need rescuing, and whether you are drawing unemployment benefit. With those we fix the RETA date, prepare the 036 with the classification and regimes that apply — including the intra-Community register if you are going to invoice abroad — and leave the quarterly calendar set up.

We do not say that waiting is always wrong or that moving early is free: we say what is at risk in each case and what it costs. It is on registering as self-employed, and the form asks for the expected start date and little else.