From people who do short-term stints of work in Germany to those who have a second home or just those who enjoy long visits, plenty of Brits take lengthy stays in Germany.

Up until now EU freedom of movement has made this a fairly simple process with no need to watch the clock on your visit or engage in complicated form-filling.

But from December 31st, when the Brexit transition period ends, there will be more restrictions on visits to Germany for British nationals.

The below applies only to people who are not an official resident in Germany and have no intention of becoming one. Those who are resident who plan to make the move before the end of the year are protected by the Brexit Withdrawal agreement and can stay in Germany as long as they want.

The rules on travel and length of visits are one of the (many) things yet to be negotiated but if nothing new is agreed then non-resident Brits in Germany will be subject to the so-called 90-day rule.

With still no trade deal agreed and a lot of really quite pressing concerns that need to be addressed in the next three months, it seems likely that the 90-day rule will become the rule from January, even if a separate bilateral agreement is reached at a later date.

READ ALSO: Q&A – What does Brexit mean for my rights as a Brit living in Germany?

So what does the 90-day rule mean?

At present the majority of EU countries operate the 90 day rule for non-EU nationals who do not have residency or a work or study visa.

So Americans, Australians, Indians and other non-EU nationals in Germany will already be familiar with this rule – people who are not resident here can spend up to 90 days out of every 180 day-period in the EU (with or without a visa depending on the country you are visiting from) but after that must either apply for residency or a work or study visa.

The rule states that over a year non-EU nationals can spend 180 days in total in Germany but not consecutively, you would have to spend time outside the EU (such as back in the UK) in between.

You can do your 90 days as one block or as several shorter trips, but in every 180 days the total number of days must not exceed 90.

It's worth pointing out that the 90 day rule applies to the total number of days for all countries in the Schengen area.

So if you have a three-month stay in Germany you wouldn't be able to – for example – go and spend a weekend with George Clooney in his Italian lakeside villa during the same 180-day period.

The EU offers this Schengen Area calculator to allow you to calculate your stay.

So after the Brexit transition period if non-resident Brits want to spend longer than 90 days at a time in Germany you really only have two options – get a visa or become a resident.

If you go for the visa option be prepared for a lot of paperwork. Photo: Unsplash

Visa

EU nationals do not require a visa for Germany. But generally speaking, all other foreigners require a visa for stays in Germany for visits lasting longer than 90 days in an 180‑day period.

There are lots of different types of visas available, from the tourist visa to a working or study permit.

Residency

If you really want to spend long periods in Germany you should probably be looking at taking up German residency before – and remember the rules will obviously be different if you move before December 31st because you will still be covered by freedom of movement.

If you move before December 31st, to become a resident you will have to register first (as everyone in Germany does when they live here).

Once you have a right of residence you will receive the residence documents from the foreigners authorities (Ausländerbehörde). But it isn't clear yet when British people will get this document.

Axel Dittmann, head of the Brexit Task Force in Germany previously told The Local: “We will provide further information when it is time to contact the foreigner's authority for the document. The fee for the residence document will most probably be similar to the one German nationals pay for their identity cards.”

British people residing in Germany will have up to six months after the end of the transition period to register for the new residence document. As for any other third-country national, this registration will be required in addition to the “Anmeldung” of your address – so don't forget to do that!

READ ALSO: Explained – How to secure permanent residency in Germany

If you want to become German, remember you cannot get dual citizenship in future. So if you become a German citizen you have to give up your British residency which has an impact on things like tax and access to the NHS.

To keep your British citizenship, you'll have to apply for German citizenship before December 31st.

READ ALSO: What you need to know about applying for German citizenship

Could you just slip under the radar?

For British people who have got used to coming and going with minimal paperwork or checks this can seem like an attractive option.

It's also true that there is likely to be a 'bedding in period' for the new rules.

However we would suggest that people don't rely on this. Unlike the pre-EU days, passports are now automatically scanned when you enter and leave the country, which makes it easy to spot over-stayers.

If you are caught over-staying your allocated 90 days you can end up with an 'over-stay' flag on your passport which can make it difficult to enter any other country, not just Germany, and is likely to make any future attempts at getting visas or residency a lot more difficult.

That said, if you've made an appointment at the Ausländerbehörde (foreigners' offices) for a residency permit, you have until whenever that appointment is to remain in Germany – even if it exceeds the three month window.