In Portugal, the client has the right to request an invoice with tax ID - always. You, as provider, have the responsibility to offer that option. But there's an art to doing this without friction: right question, right moment, smart saving. This guide shows the approach we see working in 9 out of 10 businesses.
Why ask (and why not insist)
Asking for tax ID isn't bureaucratic - it's a benefit for the client who often doesn't know they can ask. A client deducting healthcare expenses, esthetics for medical treatments, professional training - all benefit from invoices with tax ID. Not asking deprives them. Insisting, on the other hand, sounds like an aggressive sale.
When to ask (and how)
The right moment is checkout, but tone changes everything. Variations by context:
| Context | Suggested question |
|---|---|
| New client | Would you like the invoice with your tax ID? |
| Recurring client without saved tax ID | Today with tax ID on the invoice? |
| Clear company / liberal professional | Let's go with invoice using the company's tax ID, right? |
| Client who historically refuses | Simple receipt, as usual? |
| Healthcare treatment | Would you like invoice with tax ID? You can deduct on tax. |
Saving on the card: the long-term saving
This is the feature that saves hours over the year. Saving the tax ID once means in every future booking by that client, the tax ID appears pre-filled at checkout. You don't ask again.
First time client wants invoice with tax ID
At checkout, ask for tax ID and address. System validates the format.
Save on the client card
Tick Save for next time. From then on, tax ID and address appear pre-filled.
Future bookings: zero effort
Client pays, you confirm Invoice with usual tax ID? - 1 click and done.
If client changes tax ID (changed company)
Edit on the card. Old documents stay immutable (snapshot); new ones go out with the updated one.
Validating tax ID: what BookHero does for you
The Portuguese tax ID has validation rules (9 digits, first digit follows defined patterns, last digit is a check digit calculated). BookHero validates in real time:
- Confirms digit count (9 exactly).
- Confirms first digit (1-3, 5, 6, 8, 9 valid for different taxpayer types).
- Confirms check digit (last digit derived from the first 8).
- Warns if wrong before issuing the document.
Special cases: companies, foreigners, doubts
| Case | How to handle |
|---|---|
| Company client - two people come on its behalf | Ask for company tax ID (not personal). Confirm headquarters address. |
| Liberal professional uses own name + own tax ID | Tax ID starts with 1 or 2. Activity address on the invoice. |
| Foreign client without PT tax ID | Issue without tax ID (End consumer) or ask for passport for identification. |
| Client has tax ID but didn't bring it | Can give it verbally; you write and validate at the moment. |
| Client gave wrong tax ID, you noticed later | Issue credit note for the original document + new invoice with correct tax ID. |
Invoices without tax ID: perfectly legal
There's a wrong idea that invoices without tax ID are problematic - they're not. Simple receipt or invoice-receipt to End consumer is fully legal and accountable. The tax authority defines annual limits for revenue without identification - confirm with accountant.
- Simple receipt without tax ID: client who pays and doesn't want formal proof.
- Invoice-receipt End consumer: client wants proof but doesn't want to give tax ID.
- Numbering stays sequential - everything goes into the fiscal report.
- Client can always ask for tax ID later (within 15 days of issue, depending on regime).
Common errors and how to avoid them
- Not asking and assuming the client doesn't want - asking takes 5 seconds, avoids annoying questions later.
- Insisting when client says no - creates friction, sounds like pressure.
- Not saving on the card after first time - forces you to ask every time.
- Accepting tax ID without validating (paper or verbal without checking) - wrong numbers create invalid documents.
- Changing tax ID on already-issued document - can't; you have to issue credit note + new invoice.
Client education in specific sectors
In sectors where the expense is deductible, it pays to educate the client:
| Sector | Useful message to the client |
|---|---|
| Healthcare (physio, psychology, dentist) | Can deduct up to X% on tax - ask for invoice with tax ID |
| Esthetics in medical treatments | Can be reimbursed via insurance/health fund with invoice |
| Education (music lessons, training) | Education expenses deductible on tax |
| Business clients | Company can deduct VAT with company-specific invoice |
FAQ
Can I refuse to issue invoice with tax ID?
No. The client has the legal right to ask for invoice with tax ID, and you have the obligation to issue. What you can refuse is issuing without the tax ID (client doesn't give - issue simple receipt or End consumer).
What if client gives tax ID and the system says it's invalid?
Confirm with the client they didn't swap a digit. If the tax ID is really what they have, but BookHero says invalid, there's a transcription error. Refuse issuing with wrong tax ID - documents without fiscal validity cause problems for both sides.
Client pays cash - can I avoid giving tax ID?
No. The client's right is independent of payment method. A cash-paying client has the same right to invoice with tax ID as one paying by card.
What if I'm a small business with low revenue - do I really have to issue everything?
Even below tax-authority certification thresholds, you're required to issue proof for every service provided. BookHero does this simply - sequentially-numbered informational document.
Client asked for tax ID after the invoice was issued - can I add it?
Not directly. Document is immutable. Solutions: issue credit note cancelling the original + issue new document with tax ID (same date or current date depending on regime). Confirm with accountant the exact procedure for your regime.